How do you say what grade are going to in french?

There are a couple of ways to say "what grade are you going to?" in French, depending on the context and formality:

Formal:

* En quelle classe allez-vous ? (This is the most common and formal way to ask.)

Informal:

* En quelle classe tu vas ? (This is a more casual way to ask, using the informal "tu" pronoun.)

Using a number:

* En quelle année allez-vous ? (This is similar to "what year are you in?")

* Quelle année vas-tu faire ? (This is the informal version.)

Example:

* En quelle classe allez-vous l'année prochaine? (What grade are you going to next year?)

* Quelle année vas-tu faire au collège? (What year will you be in middle school?)

It's important to note that the French school system is different from the American one. French schools have classes numbered from "6ème" (sixth grade) to "Terminale" (twelfth grade), with "Collège" covering grades 6-9 and "Lycée" covering grades 10-12.

Always consider the age and context when choosing how to ask about someone's grade level.