How do you break up with a girl but stay her friend?

I go to a catholic school and my class has 18 people. I want to break up with my gf because the spark is gone but i don't want her to hate me because if she does then every other girl in my class will, and I still think that my gf is fun to be around. I am 13 and I really need your help.How do you break up with a girl but stay her friend?
You break it off honestly and in private. You tell her to her face that you aren't feeling a connection with her anymore and maybe she feels that way too? After a short speech of what went wrong, you give her a hug and walk away. Maybe even tell her its best you don't communciate for this time while you both are healing. Do not try to be friends with her, just an aquaintance. When the other girls hear how you handled it right, they'll have nothing to gripe about and then they'll start seeing you as available.