Student or Learner
The opposite of "noisy" is "quiet", and what do you think is the opposite of "calm"?
94)The students are too noisy in the classroom. <=> quiet
Or just excited. They can be happy-not-calm too. That's the problem with "opposites" -- they can sometimes go in different directions.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.