In high school they call it Senioritis..
Transitions are hard for children. He may not even understand why he feels the way he does.
He is already beginning to miss his friends, teacher, school.. the schedule will change.
He is already a little nervous about next fall because everyone is already talking about first grade and the expectations....
Try to set up some play dates with his school friends. Meet ups at the park or for swimming..
He just needs to be able to understand, people are not disappearing from his life, but taking a break..
The break will be filled with... You set up a list or a calendar, so he can look forward to fun activities. He is feeling unsure...
Children love having the heads up and schedules.. Keep him in the loop..