Can my teacher in a non-dress-code school force me to wear certain clothing for a project?

Maybe. If your teacher is asking you to wear something inappropriate you have the grounds for a complaint, but if it is part of the assignment it may teach you about the time and place you are studying about and it could be fun. Your teacher is trying to have you learn (my guess it is in history) and to get a feeling what it was like. Think about it as if you are entering a time machine. When I was teaching history I would dress up as a person from that time and take on a persona . Don't be a "stick in the mud." And have fun.