A good boyfriend - is whom will respect the fact that his girl needs to hang out with her friends. He couldn't be selfish - he mustn't get jealous when she spends more time with her friends more often in school!
He must give her some space - Give her some time to spend with her friends, instead of expecting every minute to be with her. Esp, in school. On the other hand, he can give himself some space too.
A good friend, no matter you're a girlfriend/boyfriend or not, you're still a friend to the others. Even if you have a gf/bf, you can't ignore your boundary of friends - they still need you! You can't be selfish and go on your honeymoon and ignore your friends, you gotta update them about what happened during your honeymoon! - it's hot topic - you can't just think that your honeymoon is a confidential topic, you gotta update those who care for you, who help you get together. If you have a gf/bf now, and you're starting to feel that you're losing your friends, that means you're NOT a good friend.
You rather choose to spend more time with your gf/bf - you will eventually realise that you've lost your clique of friends, you've lost their hearts, you've lost everything of them. They once wanted you so badly, but you ignored - It's hard to earn back them! Takes time, darn lots of time.
On a side note - Never ever ever be mean to your friends or play with your gf/bf while ignoring your other friends. Everything is crucial, as every act counts.