How to get him to stop being so clingy?

Tell him you like him, but you need to slow down the relationship.

Make it clear that this is _not_ a breakup. Make it clear that you like him and you want to date him.

But also start drawing some boundaries. You need alone time, and time with your friends. You never have a chance to miss one another if you see each other every minute of the day. You really like him, but you don't want to ruin anything by rushing the relationship.

If you need "girl time" with your females friends, guys would usually rather not be involved. But time alone with guy friends is a bit more complicated. I got nothin' on that front.

But overall, a few gentle boundaries might do the trick.

just talk to him and say you like him but you need time to do your own thing with your friends/study/ whatever excuse you can think of! As atomizer said, you do need to set boundaries. Even if things do get serious with this guy, you still need your own life, your own friends and interests. Then try spending less time with him, calling and texting less to actually show that you meant what you said to him previously. If he doesn't take the hint dump him!

Theres no point in repeatedly telling him to back off. If he doesn't try to cool the clinginess a bit, then there's nothing you can do. You can't force him to not be clingy so even if you do say it to him, he may (as I suspect) still be very clingy. Clingy people separate events. They'll take the hint the one particular time you say it to them but then there'll be a next time and it'll be like "grr I told you this already!" They don't realise a lot of the time how clingy they are and how repetitive their behaviour is. My friend went out with this needy guy who said he loved her after only three weeks of dating. Unsurprisingly, he had done the exact same thing with a previous girlfriend. It was a pattern and he just couldn't see that. Unless they see that, they will do it again. It might not be you but it'll be with someone else. And they'll drain all your energy because its all about "me me me" with them. Sorry to be negative but I avoid clingy people like the plague now because I know they will suck me dry. And then not appreciate anything you do for them. They have extremely high expectations from a partner. They expect you there at their every beck and call and get p*ssed off even if you have a legitimate reason for not being able to show up.

OK your guy might not be as chronic as what I mentioned above but just wanted to warn you!

Arrange to do things with your friends outside school so you won't be with him all the time, in school try and sit where there will be no room for him or stop going to lacrosse so much. The other option is to be honest with him.