A lot of children
do have separation anxiety issues, and while 8 y/o is a little old to be having this issue, it can and does happen.
However, by 8 y/o it may be necessary to investigate a little further as to why. If he is a slightly emotionally immature child, then fine, it's probably normal, but there could be issues with a teacher, or a bully, and he feels uneasy and anxious. Delve in and see.