1. I think that this is not so. After all, everything depends on the pupil himself, and not on the situation. And if the student wants to learn then he will learn.
2. Perhaps this is so, but many will not be satisfied with it. For many, summer vacations mean a lot, and even more so during this period, we are most resting. And to do and in short is not entirely correct.
3.As I said before, it all depends on the student. If he wants to learn, he will to learn regardless of what class. Mixed or not.
P.S. тут лично мое мнение.