My class have never done a project on the environment or has never done?
I would use have, because no one in class did the project, so they are treated as a single students that didn't do the project.
But maybe I should treat it as a whole, like on one did, so they are one unit?
Help! Emotion: smile
"has never done" - American English

I think of it as all members of the class working together on the project as a single unit.

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In American English, your class is singular, despite being made up of a collection of individuals, so your class has never done such a project. But, if you refer to yourselves in the first person plural, then you're plural.

You: "Our class has never done such a project"
Question: "Never?"
You: "No, we have never done such a project."
So if I think that no one have made the project ( which is a one person task, not a whole group task ), then I can say My class have?

My class have

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