Your friend is most likely worried that you'll make new friends and leave him behind, which does happen often. So I think it's important to let him know just how much your friendship with him means, and that nothing or no one could replace him.
When you get to high school, prove it by putting as much effort in your friendship as you always have. =)
Tell him that school doesn't make you want to not be friends, you do. Let him know that if he really wants to be a friend you'll be friends through highschool and beyond.
you guys might drift away and that's normal, but just tell them that you guys just need to stay in touch and stuff.. a good way to stay in touch is.. myspace or facebook
if they r a real friend than nothing will change ur friendship with eachother
if they r a real friend than nothing will change ur friendship with eachother