What is this movie called?!?

I saw this movie a few years back but cant find it. Its about a teacher moving to a new school and the school has alot of gangs and her class is really bad but tey make journals and end up being really cool by the end. I dont remember much but at sme point the teachers bf leaves her and theres a scene of two of the gangs finding each other at a gas station and one of the boys gets killed. I loved this movie but i cant find it. i thought it was like room 17 or journals of room smething. Its also based on a true story.help!!