I finished my last major testexam today, but I still have to stay in school, because we need to remove the dorm, and some students haven’t finished their tesexams yet. I finished my last major exam today, but I still have to stay in school, because we need to remove the dorm, and some students haven’t finished their exams yet.

What do you mean by "remove the dorm"?

I finished my last major test today, but I still have to stay in (remain at the) school because we need to remove the dorms, and some students haven’t finished their tests. I finished my last major test today, but I still have to stay in (remain at the) school because we need to remove the dorms, and some students haven’t finished their tests.

By "remove" do you mean pack up your items? If so, a better sentence would be, "because we need to pack up the dorms".

I finished my last major test today but I still have to stay inat school because we need to removvacate the dorm, and some students haven’t finished their tests. I finished my last major test today but I still have to stay at school because we need to vacate the dorm, and some students haven’t finished their tests.

I’m guessing you mean “vacate.”

I finished my last major test today but I still have to stay in school because we need to removeclean the dorm, and some students haven’t finished their test yet. I finished my last major test today but I still have to stay in school because we need to clean the dorm, and some students haven’t finished their test yet.