Some children are worriers and some family situations promote worry. Try to help a child understand that it isn't his job to worry about adult problems. Get help if your family is being overwhelmed by such problems.
Everyone has a late night now and then. It is a continuous lack of sleep that exacerbates school problems. If your child is really having difficulty at school, remember to check how much sleep they are getting. Ten or eleven hours of sleep can make a world of difference in your child's world.