1. He is so distracted in class.

Question

2. He is focused during the class.
3. They are distracting in class.
4. They are distracted in class.
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Can we use all the expressions? Do you have some more expressions-adjectives- you use when many troublemakers make noise in class?

Answer 1

All four are good sentences. Note that "distracted" is a verb. "Focused' is also a verb. "Distracting" is a gerund. None of them are adjectives. Someone making noise in class might be said to be disruptive, disrupting the class. We might say the disruptive or distractive students made too much noise in class.

Answer 2

Sorry to disagree, but in those four sentences, these words are both being used as participles or verbal adjectives: "distracted" and "focused" are past participles, and "distracting" and "focusing" are present participles.

Here's a good webpage that explains and gives examples of English verbs' principal parts:
http://englishplus.com/grammar/00000357.htm

The sentences, as you have written them, though, are good ones, as Reed has said.