The first day of school can be both a positive and negative experience for kids. While it's fun to re-connect with friends they haven't seen over the summer, it's always a little scary to have new teachers and not know exactly what to expect. Starting a new school is the scariest thing of all.
There are lots of books for little kids about the first day of school and I read many of them to my grandson before he entered preschool. His first day went smoothly because he knew what to expect and the teacher was impressed with how well he adjusted. But the second day wasn't so good. He had no idea there would be a second day and even more after that.
When I was a little kid I had to enter new schools several times after the school year had already begun and everyone else had already gotten used to the routine and knew the teachers and each other. That was very scary for me.
But being new is probably harder for older kids because the social hierarchy has already established and they have to deal with bullies. Here's a website that can help a lot with the bullying problem. www.bullies2buddies.com While the techniques suggested here are different than those suggested in many bully prevention programs and may not always be successful, I've seen them work many times. I think it would be a big help to kids starting new schools or a new school year to know about them.