The free tools you actually have

You do not need to buy anything

Every major model has a free tier, and every free tier runs in a phone browser. If you have a phone that can open a web page, you have access to the same underlying models a paid user has, with two differences: a cap on how many messages you can send before it slows you down or switches to a smaller model, and fewer extras like long file uploads.

For a teacher generating a worksheet, a set of misconceptions and a parent letter in an evening, the cap almost never bites. Where it does, the fix is to wait, or to have a second tool open.

The realistic list

Here is what is available at no cost as of this writing. Products change names and limits often, so treat the shape as stable and the details as something to re-check.

• ChatGPT (OpenAI). Free tier includes the main model with a message cap, image upload, voice, and web search. Works in a browser without the app. Basic chat and web search work without an account; voice and saved history need one, which can be an email address or, in some countries, just a phone number.
• Gemini (Google). Free with any Google account. Tightly tied to Docs, Sheets and Gmail, which matters if your school runs on Google Workspace. Also inside Android as the assistant.
• Claude (Anthropic). Free tier with a usage limit that resets every five hours. Strong on long documents and careful writing. Account required; terms are for adults.
• Copilot (Microsoft). Free, built into Edge and Windows, uses OpenAI models underneath. If your school runs on Microsoft, this is the one already installed.
• Meta AI inside WhatsApp. No new account, no new app, works on the data plan you already pay for. The model is Meta’s Llama. It is weaker than the others on long, careful tasks and stronger than all of them on one thing: it is already on the phone of nearly every teacher in India, Nigeria, Kenya and Brazil.
• DeepSeek and other Chinese models. Free, capable, and hosted in China, which is a data-location question your school may have a view on.

The open-source route also exists: models like Llama and Qwen can be run on your own computer with free software such as Ollama or LM Studio. This needs a laptop with at least 8 GB of memory and gives you a weaker model in exchange for nothing leaving the machine. It is the right answer for a school that cannot send any data out, and the wrong answer for a teacher with a phone.

The one setting

Most consumer chatbots default to using your conversations to improve their models. That means the essay you pasted, the student name you forgot to remove, the parent complaint you asked for help with: all of it may be read by people at the company and folded into future training.

Before you paste anything about a student, find the setting. In ChatGPT it lives under Settings, then Data controls, labelled something like “Improve the model for everyone”. In Gemini it is under Activity. In Claude it is a privacy setting. Turn it off. This does not make the tool private (the company still receives and stores what you type), but it takes your students’ work out of the training pipeline.

Then treat what you paste the way you would treat what you say in a staffroom with the door open. First names and no surnames. No addresses. Nothing you would not want a stranger at the company to read.

Browser or app

Use the browser. The apps ask for permissions you do not need to grant, take storage you may not have, and on a shared family phone leave a logged-in account for whoever picks it up next. A browser tab you close is gone. If the phone is shared, use a private window.

The limitation

A free tier is a queue. When demand is high, the service quietly gives you a smaller, faster model, and answers get shallower without any notice. If a tool that was sharp at seven in the morning is producing thin work at nine in the evening, that is usually why. Nothing you did changed. Ask again tomorrow, or switch to a second tool for the rest of the session.

The other limit is the message cap itself. It resets on a schedule, typically every few hours, and it is per account, so a department sharing one login will hit it by lunchtime. Each teacher needs their own.

What to do tonight

Open one of these in your phone browser. Turn off training. Ask it for five wrong answers your students give about something you taught this week, and see how many you recognise. That is the whole setup, and it took ten minutes.