The evidence
Across every major U.S. school attack since Columbine, we could not find a single victim killed behind a locked classroom door whose lock held.
That sentence is checked against the official investigations, incident by incident, below. The deaths that did happen behind closed doors came through glass, never through the lock. And roughly nine in ten deaths happened where no locked classroom door stood between the attacker and the victim.
What the authorities say
The commissions, fire marshals and researchers agree
The Commission cannot emphasize enough the importance of this recommendation. The testimony and other evidence presented to the Commission reveals that there has never been an event in which an active shooter breached a locked classroom door.
Sandy Hook Advisory Commission, Final Report, Recommendation No. 1, March 2015. Source (p. 24)
No mechanical breach in the dataset was accomplished by defeating a locking mechanism. In every successful case, the perpetrator bypassed the lock by destroying or shooting through glass. Flush doors with functional locks were never successfully breached.
ALERRT Center, Texas State University, "The Role of Locked Doors and Access Control in School‑Based Active Shooter Events," 54 events, 2000–2025, May 2026. Source (pp. 30–31)
Had school personnel locked the doors as the school's policy required, that could have slowed his progress for a few precious minutes, long enough to receive alerts, hide children, and lock doors; and long enough to give police more opportunity to engage and stop the attacker.
Texas House of Representatives Investigative Committee on the Robb Elementary Shooting, July 2022. Source
Compliance, not hardware, is the most common failure mode. The data consistently show that the gap between having security hardware and using it is one of the most significant vulnerabilities in school safety.
ALERRT Center, 2026. 62% of the doors attackers encountered were unlocked or propped open. Source (p. 28)
All recommend classroom doors that are closed and locked when occupied, lockable without stepping into the hallway, unlockable from outside by authorized people, and always openable from inside.
The honest number
128 deaths in 19 K‑12 attacks. Where were the victims?
We tallied every death in the major U.S. K‑12 school shootings from Columbine (1999) through September 2026 using the official investigation for each, excluding attackers. Virginia Tech is excluded as higher education. The full incident table is below.
We do not claim "99%." The 89% includes people in hallways and cafeterias, where a classroom lock is not where they were, and a lock does not stop bullets through glass. What the record supports is narrower and stronger: the lock has never been the thing that failed.
Why time is the whole problem
Attacks are over in minutes. The door has to already be locked.
83% end within five minutes
Of 41 targeted K‑12 attacks studied by the Secret Service, 83% lasted five minutes or less, 68% two minutes or less, and 44% ended within one minute. None was ended by police arriving from off campus.
60% end before police arrive
In the FBI's study of 160 active shooter incidents, 69.8% of those with a known duration ended in five minutes or less, and 60% ended before police arrived.
95% are current students
In the Secret Service study, 95% of attackers were current students of the school. They are already inside. The perimeter and the front‑door scanner are behind them.
The human step fails under fire
In a randomized trial with blank gunfire as the stimulus, people trying to secure a classroom door 35 feet away failed with a key‑operated lock 31% of the time, and took over 11 seconds when they succeeded. A push‑button lock failed 5% of the time. A door that is locked by default takes zero seconds and cannot be forgotten.
Martaindale, Sandel & Duron, Journal of Mass Violence Research (2023)
What the investigations found on the ground
- Uvalde: teachers propped exterior doors with rocks, left interior doors unlocked for convenience and used magnets to defeat latches. Room 111's lock "was widely known to be faulty, yet it was not repaired." The Department of Justice found "a culture of complacency regarding locked‑door policies." All 21 people killed were in rooms 111 and 112.
- Sandy Hook: every classroom door locked only from the hallway with a key. The substitute teacher in Room 8 had no keys. Twenty children died in rooms 8 and 10.
- Parkland: locks required a key on the hallway side. The attacker never entered a classroom; every round into a room went through the door or its window. Only 2 of 30 classrooms had a marked hard corner.
- Oxford: doors were locked. The shooter "was unable to actually enter any of the classrooms." The four students killed were in a hallway and a bathroom.
- Evergreen (2025): lockdown 42 seconds after the first shot. The attacker spent three minutes trying doors and could not get back in. The sheriff credited locked doors with preventing many more injuries.
Incident by incident
Were the doors locked? Did the attacker get into a classroom?
Compiled from the official investigation where one exists. K = killed (excluding the attacker), W = wounded by gunfire.
| Incident | K / W | Classroom doors locked? | Entered a locked classroom? | Where the harm happened | Source |
|---|---|---|---|---|---|
| Columbine HS, CO, 1999 | 13 / 20+ | Students locked down and barricaded | No | Outside, hallway, library | Summary |
| Red Lake HS, MN, 2005 | 7 / 7 | First classroom was locked | Yes, by shooting out the glass beside the door and reaching in. A second attempt to shoot a lock failed. | Entrance; inside the breached classroom | ALERRT pp. 31, 61 |
| West Nickel Mines, PA, 2006 | 5 / 5 | One‑room schoolhouse; attacker walked in | n/a | Inside the single room | Summary |
| Sandy Hook ES, CT, 2012 | 26 / 2 | No. Doors locked only from the hallway with a key; substitute had no keys | Entered two unlocked rooms | Hallway; rooms 8 and 10 | State's Attorney |
| Marysville‑Pilchuck HS, WA, 2014 | 4 / 1 | n/a | No | Cafeteria | Summary |
| Aztec HS, NM, 2017 | 2 / 0 | Yes. Attacker shot a door lock and could not get in | No | Bathroom, hallway | ALERRT p. 31 |
| Marjory Stoneman Douglas HS, FL, 2018 | 17 / 17 | Key‑locked from the hallway; status of doors fired on unknown | No. "Never entered a single classroom." All rounds through doors or door windows | Hallways, stairwell; inside rooms through door glass | MSD Commission |
| Santa Fe HS, TX, 2018 | 10 / 13 | Attacker was a student already inside the art rooms | Began inside | Art classrooms and closet | Summary |
| Oxford HS, MI, 2021 | 4 / 7 | Yes | No. "Unable to actually enter any of the classrooms" | Hallway, bathroom; one teacher wounded through an office door | Guidepost report |
| CVPA HS, St. Louis, MO, 2022 | 2 / 4 | Building and classroom doors locked | Yes, through glass (sources differ on one door) | Dance studio; room 323 | ALERRT p. 30 |
| Robb ES, Uvalde, TX, 2022 | 21 / 17 | No. Lock on room 111 known faulty; exterior and at least 8 interior doors unlocked | Entered unlocked rooms 111/112 | All inside rooms 111/112 | DOJ CIR |
| The Covenant School, TN, 2023 | 6 / 0 | Exterior glass doors shot out; classrooms shut and locked | No occupied classroom | Hallway and stairwell | MNPD summary |
| Perry HS, IA, 2024 | 2 / 6 | Attacker shot a locked door, tried the handle; it held | No | Cafeteria before school | ALERRT p. 31 |
| Apalachee HS, GA, 2024 | 4 / 9 | Shooter's own classroom auto‑locked behind him; a student saw the rifle and did not open | Entered one nearby classroom (door status not established) | That classroom; a teacher at his doorway; hallway | ALERRT p. 17 |
| Abundant Life, Madison, WI, 2024 | 2 / 6 | Attacker was a student seated in the room | Already inside | Study hall | Summary |
| Antioch HS, Nashville, TN, 2025 | 1 / 1 | n/a | No | Cafeteria | Summary |
| Annunciation, Minneapolis, MN, 2025 | 2 / 27 | Attacker never entered; fired through church windows | No | Church pews | Summary |
| Evergreen HS, CO, 2025 | 0 / 2 | Yes. Lockdown in 42 seconds | No. Tried several doors for 3 minutes and failed | One inside, one outside | Jefferson County Sheriff |
| Westwood Hills ES, VA, 2026 | 0 / 1 | Adult outsider forced entry to the building | No | Staff member wounded; ended in library | VPM |
Virginia Tech (2007), excluded from the K‑12 tally, is the clearest natural experiment: identical unlockable doors; the one room barricaded with a table took seven shots through the door and had zero casualties; the three un‑barricaded rooms had 27 deaths. Virginia Tech Review Panel.
The counterexamples, stated plainly
What a lock does not do
- It does not stop bullets. At Parkland, six were killed and thirteen wounded inside classrooms through door windows. At Red Lake and CVPA, attackers reached in through shot‑out glass. Vision panels, security film and hard corners matter alongside the lock.
- It cannot help when the attacker is already in the room. Santa Fe and Abundant Life were students inside the classroom when they began. Threat assessment and reporting are the prevention layer.
- It does not cover hallways, cafeterias or fields. Thirty‑eight percent of the deaths in the tally happened in open spaces.
- A critic's view. David Riedman of the K‑12 School Shooting Database argues locked doors have not changed how often attacks involve multiple rooms, and points to Parkland students locked out of rooms. We think the answer to "locked out" is a door that opens for the students who belong there, which is exactly what ClassLock is. Read his analysis.
What ClassLock changes
From "can be locked" to "is locked"
Seventy‑six percent of U.S. public schools now report classrooms that can be locked from inside. The investigations show that "can be" is not the problem. Doors that could be locked were propped, keyed from the hallway, defeated with magnets, or left open because answering the door all day is disruptive.
ClassLock removes the step. Doors are locked by default during class, open with a tap for the students on that period's roster, and never require a teacher to leave the room or find a key. Lockdown comes from the office, a panic alert or a button inside the room, and the door sensor reports which rooms are actually closed.
NCES, Digest table 233.50.
Every investigation ends at a door. Start there.
Primary sources used on this page
- Sandy Hook Advisory Commission, Final Report (March 2015). https://portal.ct.gov/-/media/Malloy-Archive/Sandy-Hook-Advisory-Commission/SHAC_Final_Report_3-6-2015.pdf
- Office of the State's Attorney, Danbury, Report on the Shooting at Sandy Hook Elementary School (Nov 2013). https://portal.ct.gov/-/media/DCJ/SandyHookFinalReportpdf.pdf
- ALERRT Center, Texas State University, The Role of Locked Doors and Access Control in School‑Based Active Shooter Events (May 2026). https://alerrtresearch.org/resources/reports/report_2026_sia_locked_doors.pdf
- U.S. Department of Justice, Critical Incident Review: Active Shooter at Robb Elementary School, Executive Summary (Jan 2024). https://portal.cops.usdoj.gov/resourcecenter/content.ashx/cops-r1143-pub.pdf
- Texas House of Representatives, Investigative Committee on the Robb Elementary Shooting, Interim Report (July 2022). https://house.texas.gov/media/pdf/committees/reports/87interim/Robb-Elementary-Shooting-Report-070722.pdf
- Marjory Stoneman Douglas High School Public Safety Commission, Initial Report (Jan 2019). http://www.fdle.state.fl.us/MSDHS/CommissionReport.pdf
- Guidepost Solutions, Oxford Community Schools Independent Investigation (Oct 2023). https://schoolshooters.info/sites/default/files/FINAL-REPORT-OCS-Investigation.pdf
- Metropolitan Nashville Police Department, Covenant Investigative Case Summary (Apr 2025). https://www.nashville.gov/sites/default/files/2025-04/Covenant_Final_Summary.pdf
- U.S. Secret Service NTAC, Protecting America's Schools (2019). https://www.secretservice.gov/data/protection/ntac/usss-analysis-of-targeted-school-violence.pdf
- FBI, A Study of Active Shooter Incidents in the United States Between 2000 and 2013 (2014). https://www.fbi.gov/file-repository/reports-and-publications/active-shooter-study-2000-2013-1.pdf
- Martaindale, Sandel & Duron, Successfully Securing a Classroom Door in a Lockdown, Journal of Mass Violence Research (2023). https://jmvr.org/2023/07/successfully-securing-a-classroom-door-in-a-lockdown-evaluating-two-types-of-door-locks/
- Jefferson County Sheriff's Office, Evergreen High School update (Sept 2025). https://www.jeffco.us/m/newsflash/Home/Detail/2472
- NCES, Digest of Education Statistics 2023, Table 233.50. https://nces.ed.gov/programs/digest/d23/tables/dt23_233.50.asp
- NASFM, White Paper on Classroom Door Security and Locking Hardware (July 2024). https://lifeboltlocks.com/wp-content/uploads/2024/11/NASFM-2024-School-Door-Locking-Document-Approved-7-28-2024-1.pdf