I hope not. Depression is rather common, and if it were a cause for exclusion from school, i suspect we would have a lot more children looking for vaction days by complaining they are not in the mood. More seriously, children are entitled to a free and appropriate education and this would be a violation of the ada. Now if the child is irritbable threatens/hurts other children, it is another thing.
No. But your child can get kicked out for behaving badly, acting out in violent or unacceptable ways, or failing classes because he/she is depressed. A child who is depressed but sits quietly and doesn't get in trouble is not going to get kicked out; but that child needs help just as much as the child who is getting in fights.