Refused to go to the school

Recently Ethan refused to go to school after the one week National Holiday. He will cry when mummy left him with the teacher. Mummy had been asking the teacher why like that? Teacher said probably Ethan is a slow reaction kind of person. At first when he came to school everything was new to him so he has no time to think of other things other than exploring the new environment. Now he is familiar with it then he has spare time to think of other things like he is away from his parents. Hoped that the kind of situation will not be prolonged ...?