I don't know if "legally" school staff can ask children about their outside of school activities and whereabouts but it certainly happen everyday in school. During circle time, children are always asked "what did you do on the weekend?" "where did you go after school yesterday"? "who did you go with?", etc.
One time a child forgot to bring her homework, I overheard the teacher asking if she stayed with her mom or dad last night. I thought that the question was a bit personally. But I guess the teacher wanted to know the information so that she knows who to call about the missing homework.