I also find that some of her teachers seem unwilling to help or offer her any advice. I have called the teachers on several occasions and they assure me that everything is fine. Set the timer. Make jokes about the situation, fool around like the boys in her class who may be distracting her. This should help her adjust to the test-taking at school, but tests will probably always make her feel tense.
Some people are like that.
He will be 13 and has been accused of disrupting the entire class. Now, he has been asked out of the school. Boys and girls change a lot between 12 and 15, but seldom enough to get them tossed out of school, or even suspended. I'd have a confidential talk about it with the pediatrician and then make an appointment for him to give your son a full check-up, including drug tests. I hate to say it, but that's the first thing to look for when behavior changes precipitously, especially if his friends are misbehaving too or seem different.