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Detection tells you there is a problem. A locked door stops it.
Schools are spending millions on systems that try to spot a weapon. Most of those systems have missed real weapons in real schools, slow every student down every morning, and still leave every classroom door open. Here is the record, with sources, and what it costs.
Side by side
What each approach actually does
| Approach | What it stops | What it misses | Typical cost | Staffing | Student experience | Privacy |
|---|---|---|---|---|---|---|
| AI weapons scanners (Evolv Express and similar) |
Some concealed firearms, at a screened entrance, during screening hours | Large knives missed 42% of the time in independent testing; micro‑compact pistols 8%; anything through an unscreened door or after screening ends | Lease, about $1,650 to $3,200 per unit per month on 4‑year terms; district contracts of $2.5M to $20M | A screener at every lane plus secondary search; one district budgets $250,000 a year in screeners for one school | Lines; laptops carried in hand; binders banned; 30% of entries alarm in one city | Body scan with camera image; facial recognition options |
| AI gun‑detection cameras (ZeroEyes, Omnilert, Volt) |
Nothing physically. Alerts a human when a drawn, visible gun is inside a camera's view | Concealed guns; guns outside camera view or too far away; knives; everything before the weapon is drawn | $168 to $592 per camera per year; $1M+ district‑wide deals | Vendor operations center plus the school's own response | None at entry | Continuous AI analysis of every camera feed; a Doritos bag triggered armed police on a student |
| Walk‑through metal detectors | Metallic weapons at a staffed lane | Side doors, propped doors, non‑metallic weapons, anything after screening ends | $1,500 to $25,000 per unit; labor dominates | Two or more staff per lane plus bag check | Lines at arrival; bag searches; lower perceived safety in studies | Bag searches; visible policing |
| School resource officers | Fights and some non‑gun violence; response after an attack starts | Attacks are mostly over in under five minutes; one officer, one location | $77,000 to $168,000 per officer per year | The officer | Neutral to negative; higher suspensions and arrests in studies | Low |
| Panic buttons (Alyssa's Law systems) |
Nothing physically. Speeds notification and lockdown orders | Any door that is still unlocked when the alert goes out | Subscription; grants often cover it | None | None | Low |
| ClassLock schedule‑aware classroom access control |
Entry into any classroom by anyone not credentialed and scheduled for it, all day, with no staff action | Does not detect weapons; does not cover hallways, cafeterias or outdoor areas; does not stop an attacker already inside a room | About $2,200 per door installed, one time, plus $250 to $400 per door per year. Estimator | None at the door. IT and facilities administer it. | Tap a badge; no lines, no searches | No cameras, no AI, no biometrics. Credential and schedule data only. |
Figures and findings are drawn from the sources listed at the bottom of this page. ClassLock complements threat assessment, reporting and panic alerts; it does not replace them.
The record
AI weapons detection: what the FTC, the tests and the incidents show
The FTC action, November 2024
The Federal Trade Commission charged that Evolv falsely advertised that its scanners detect all weapons, ignore harmless items, and cut labor costs by 70% compared with metal detectors. The Commission vote was 5 to 0. The order lets K‑12 schools that signed between April 2022 and June 2023 cancel their contracts. There was no monetary penalty and no admission.
Utica, New York, October 2022
A student walked through an Evolv scanner at Proctor High School carrying a large knife that was not detected and stabbed a classmate. The district replaced the scanners at the high school with conventional metal detectors.
Antioch High School, Nashville, January 2025
A student shot and killed a classmate in the cafeteria. The school's camera‑based AI gun‑detection system did not alert; the district and the vendor say the shooter was outside the cameras' effective view. The school had no metal detectors. Weapons scanners were installed only after the shooting. A lawsuit over the system's disclosed limits was filed in 2026 and is unresolved.
Independent testing
In a test obtained by IPVM and reported with the BBC, the scanner failed to detect large knives in 42% of walkthroughs and detected micro‑compact pistols 92% of the time. IPVM
False alarms at scale
- New York City's 2024 subway pilot: 2,749 scans, 118 false positives, zero guns. City & State
- Rockford, Illinois: more than 85,000 false alerts on laptops in one school year; five knives recovered. NBC Chicago
- Baltimore City: about 30% of roughly 14,000 daily entries trigger an alert, almost all laptops and drink containers. CBS Baltimore
What it costs
- Prince William County, Virginia: $10.7 million, four years, 81 units, plus staff stipends to arrive early and run them. Prince William Times
- Gwinnett County, Georgia: about $20 million for middle and high schools. Undark
- Granite District, Utah: a $280,000 four‑year lease at one high school, plus $250,000 a year in contracted screeners to run it. KSL
- Clarksville‑Montgomery County, Tennessee dropped its scanner lease in 2026 for units that cost $15,000 to $20,000 to buy outright. WSMV
About The Covenant School (Nashville, 2023). No detection technology was present. The shooter fired through locked glass exterior doors to get in. The lesson there is about the perimeter, not about detection, and it is why a second layer inside the building matters.
Metal detectors
Easily bypassed, hard to staff, and students feel watched
A systematic review in the Journal of School Health found insufficient evidence that metal detectors reduce violent behavior, and several studies in it found lower student perceptions of safety where detectors are used. Detectors only work at the lane that is staffed. A propped side door, a dismissal‑time gate or a weapon stashed on campus the day before goes around them.
The real cost is people. Each lane needs trained staff and a bag check, every morning, for the whole year. South Carolina's statewide estimate put equipment in the low tens of millions and staffing at up to $98 million a year.
Hankin, Hertz & Simon, Journal of School Health (2011) · Wilder Research literature review
Officers and alerts
Necessary, and not enough on their own
School resource officers cost $77,000 to $168,000 a year all‑in and can be in one place at a time. A national study found that school police did not prevent shootings or gun incidents, while increasing suspensions and arrests. At Apalachee High School in 2024 the panic alert worked as designed and four people still died, because an alert calls for help; it does not lock a door.
ClassLock is the layer that does. It takes a lockdown trigger from a panic‑button system and holds every classroom door while the officer and the police are moving.
Why the perimeter cannot be the whole plan
Ninety percent of attackers were students of the school they attacked.
In the Secret Service's study of 41 targeted school attacks, nine in ten attackers were current students. They had badges. They knew the side doors. They walked past the scanner every morning. Eighty‑three percent of those attacks were over within five minutes, and 44% within one minute.
Parkland, 2018
The shooter entered through an open, unstaffed gate at dismissal and an unlocked building door. He never entered a single classroom; he fired at people in his line of sight in hallways and through classroom door windows.
Uvalde, 2022
Staff routinely propped doors. The lock on room 111 had been reported faulty months earlier with no work order. The door was never locked.
Apalachee, 2024
The shooter, an enrolled student, returned to a locked classroom door, could not get in, and fired into the room next door instead.
Sources: U.S. Secret Service NTAC, Protecting America's Schools (2019); ABC News on the MSD Commission; Texas Tribune on the Texas House report; FOX 5 Atlanta timeline.
Five‑year cost, one high school
Same five years. Very different outcomes.
A 1,500‑student high school with 60 classroom doors and three entrances. Planning figures only; every district's numbers differ.
Scanner line: 4 units at $2,500 per month for 48 months plus 8 screeners at $18 per hour, 2 hours per day, 180 days, 5 years. Metal detector line: 4 units at $15,000 plus the same staffing. SRO line: $110,000 per year. ClassLock line: 60 doors at $2,220 installed plus 12% contingency and $300 per door per year. Run your own numbers.
Honest limits
What ClassLock does not do
It does not detect weapons.
It does not need to. It denies entry to rooms regardless of what someone is carrying.
It does not cover open spaces.
Cafeterias, gyms, hallways and fields need other measures, including threat assessment and reporting, which the Secret Service identifies as the primary prevention lever.
It has no incident record yet.
ClassLock is a new product. The evidence for locked classroom doors is strong; the evidence for ClassLock specifically will come from pilots. We will publish drill data as districts allow.
Put the doors in the plan.
Bring your current safety budget. We will show you what a classroom‑door layer adds and what it replaces.
All sources for this page
- FTC, "FTC Takes Action Against Evolv Technologies for Deceiving Users About Its AI‑Powered Security Screening," Nov 26, 2024. https://www.ftc.gov/news-events/news/press-releases/2024/11/ftc-takes-action-against-evolv-technologies-deceiving-users-about-its-ai-powered-security-screening
- IPVM, "BBC / Evolv testing." https://ipvm.com/reports/bbc-evolv
- City & State NY, NYC subway pilot results, Oct 2024. https://www.cityandstateny.com/politics/2024/10/results-are-evolv-gun-scanners-recover-zero-guns-subways/400522/
- NBC Chicago, Rockford false alerts. https://www.nbcchicago.com/investigations/settlement-approved-evolv-weapons-detector-company-ftc/3623124/
- CBS Baltimore, false alarm rate. https://www.cbsnews.com/baltimore/news/baltimore-ai-weapsons-detection-maryland-schools-false-alarm/
- Prince William Times, board approval of $10.7M lease, May 2023. https://www.princewilliamtimes.com/news/school-board-approves-evolv-weapons-detection-systems-for-middle-high-schools/article_e9f45ac6-eac1-11ed-9734-d79fbcfb4373.html
- Undark, "As more schools turn to AI weapons detection, questions persist," Feb 2026. https://undark.org/2026/02/13/as-more-schools-turn-to-ai-weapons-detection-questions-persist/
- KSL, Granite School District costs. https://www.ksl.com/article/51212747/ftc-settles-with-weapons-detector-company-used-in-utah-schools
- WSMV, Clarksville‑Montgomery drops Evolv, Mar 2026. https://www.wsmv.com/2026/03/05/middle-tn-school-district-drops-evolv-weapons-detection-systems-more-cost-efficient-security/
- WIBX, Utica phases out scanners. https://wibx950.com/utica-schools-will-phase-out-new-3-million-weapons-detector/
- NBC News, Antioch High School AI detection. https://www.nbcnews.com/news/us-news/ai-weapon-detection-system-antioch-high-school-failed-detect-gun-nashv-rcna189025
- KCUR, ZeroEyes and false‑alarm rates. https://www.kcur.org/education/2025-05-03/kansas-ai-guns-schools-zeroeyes
- ABC News, Covenant School doors. https://abcnews.com/US/nashville-shooting-shows-school-doors-security-weakness-expert/story?id=98178022
- Hankin, Hertz & Simon, "Impacts of Metal Detector Use in Schools," Journal of School Health (2011). https://eric.ed.gov/?id=EJ917962
- Sorensen et al., school police study. https://files.eric.ed.gov/fulltext/ED616763.pdf
- Peterson et al., JAMA Network Open (2021). https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2776515
- U.S. Secret Service NTAC, "Protecting America's Schools" (2019). https://www.secretservice.gov/data/protection/ntac/usss-analysis-of-targeted-school-violence.pdf
- Texas Tribune, House investigative committee takeaways, July 2022. https://www.texastribune.org/2022/07/17/house-uvalde-investigation-takeaways/
- ABC News, Parkland security failures. https://abcnews.com/US/security-failures-parkland-school-shooting-included-unlocked-doors/story?id=60056864
- FOX 5 Atlanta, Apalachee timeline. https://www.fox5atlanta.com/news/apalachee-high-school-shooting-timeline-sept-4-2024.amp