'You take my class.' would make sense only if it's a teacher saying it to a student, but that's probably not the case here because the subject is addressed with 'usted'. Assuming it's a student talking to a fellow student, wouldn't 'You're in my class' be a more sensible translation?
"In Spain, the basic rule is that tú is used with people you are on a first name basis with. You'll use it with friends, family, children and animals, among youth, and even in some prayers (prayers are filled with grammatical exceptions in Spanish, so just memorize as necessary). And young people are tending to use tú over Usted in many situations that older folks would not."
If I'm reading that correctly, a professor addressing an adult student using "usted" would be normal or at least not unusual. Most of my professors call me Jeff, but you still get the occasional guy who insists on referring to everyone as "Mr. Lastname".
In the UK, "to take a class" means "to teach a group of students". A teacher could say this to another teacher who has the same group of students. Elsewhere in the world, "to take a class" means "to learn a subject". Rich ambiguity!
I'm from the UK too, but I would say "I'm taking a class in Spanish" -- meaning that I was learning Spanish.
Sometimes, a student will take another student's class (for them). Could be one of those shady scenarios
"You took my class" would be "Usted tomó mi clase". Or "Tú tomaste mi clase".
Could this sentence be a command? If so, shouldn't an implied "you" be accepted? In other words why wouldn't "Take my class" be accepted?
tu tomas = 2nd person informal / Usted toma = 2nd person formal (which uses the 3rd person singular endings)