"Best AI checker" is one of the most searched phrases by teachers right now. The honest answer is uncomfortable: no AI detector is reliable enough to prove a pupil used AI. Here is what the tools can and cannot do, and what works better.
The short answer
AI checkers — tools that claim to detect whether text was written by AI — produce a probability, not proof. They flag genuine work as AI (false positives), miss AI text that has been lightly edited, and are particularly unreliable for pupils writing in a second language or in a formal, simple style. No detector should be used as the sole basis for an accusation.
The checkers teachers ask about
| Tool | What to know |
|---|---|
| Turnitin AI writing indicator | Built into a platform many secondary schools already use. Turnitin itself says scores should not be the only evidence. |
| Free online checkers (GPTZero, ZeroGPT and similar) | Variable accuracy; results differ between tools on the same text. Pasting pupil work into free tools also raises data questions. |
| Built-in checkers in learning platforms | Convenient, but the same limitations apply. See Toddle for one example of a platform with AI features. |
Our view: if your school already has Turnitin, use its indicator as one signal among several. Do not pay for a standalone AI checker expecting certainty.
Why they fail
- Good writing looks "AI-like". Clear, structured, grammatical prose scores as AI, which penalises strong writers.
- EAL pupils are flagged more often. Simpler sentence structures trip detectors.
- Easy to defeat. Paraphrasing tools and light editing drop scores dramatically.
- No audit trail. A score cannot be explained or defended in a complaint.
Worried about AI in pupils' work?
Tell me what you're trying to sort out — a tool, a policy, a parent question, a workload problem — and I'll give you a straight answer.
What JCQ expects
For coursework and non-exam assessment, JCQ requires teachers to be confident the work is the candidate's own and to monitor it as it is produced. AI misuse is malpractice. But JCQ does not require detectors — it expects teacher judgement and process. See JCQ guidance on AI in assessments explained.
What works better than a checker
- Know the pupil's usual work. Sudden changes in style are the strongest signal.
- Look at the process. Drafts, version history and work done in class.
- Talk to the pupil. "Walk me through how you wrote this."
- Design tasks that resist AI. Personal, local and class-specific content. See designing AI-resistant homework.
- Teach honest AI use. Clear rules and a culture where AI help is declared.
We go deeper on the signs teachers look for in how do teachers check for AI? and should schools use AI detectors for coursework?
If you do use a checker
- Treat the score as a prompt for a conversation, never a verdict.
- Never paste named pupil work into free online tools.
- Write the limits into your academic integrity policy.
- Tell pupils and parents how the school uses it.
Where AskColin comes in
Rather than buying a detector, most schools need two things: clear rules pupils and parents understand, and staff who know what to look for. I write the first and train the second — an academic integrity section for your AI policy and a half-day staff session for £395. Cheaper than a year of detector licences, and it actually works.
Frequently asked questions
What is the best AI checker for teachers?
None is reliable enough to prove AI use. If your school has Turnitin, its AI indicator can be one signal among several, but teacher judgement, drafts and a conversation with the pupil work better.
Are AI detectors accurate?
No. They produce probabilities, flag genuine work as AI, miss edited AI text, and are less reliable for pupils writing in a second language.
Does JCQ require AI detectors?
No. JCQ requires teachers to be confident work is the candidate's own and to monitor its production, which relies on process and judgement rather than detectors.
Can a school discipline a pupil based on an AI checker score?
Relying on a score alone is risky and hard to defend. Schools should gather other evidence and follow their policies.
Is it safe to paste pupil work into free AI checkers?
Pupil work is personal data. Pasting it into free online tools without school approval raises data protection concerns.