How do teachers actually check for AI in essays?

Curious how teachers actually check for AI use beyond just running a detector tool. I feel like there’s more to it than just plugging text into Turnitin or GPTZero.

I’ve heard some teachers compare writing style against earlier assignments or ask follow-up questions in class to see if students can explain their own reasoning. Asking partly out of curiosity and partly because I want to understand what’s actually being evaluated before I submit anything.