should i end the friendship?

I have a friend that I have known for 4 years. We were really good friends but I really don't understand what is going on. I used to go to this house very often but I turn him down now becausd of what I have noticed. I have noticed that he has started hanging out with bad people at school. We used to hangout at school everyday but he has ditched me ever since another of our friends moved. At school he has no idea who I am. Ever since he started hanging out with the crackheads he pretends like I don't exist at school. I pass by him and his friends in the hallways and he pretends not to see me. I have gotten into a new group of friends at school who I actually really like alot. I am a very calm, funny and family oriented person so I seek people who have these values. When ever I hang out with my new group his new friends tease me and he also joins in which really makes me mad. To add to this, I have a religious class on Wednesday and he is in my class. During the class he talks to me alot and actually gets along with the group im in. he invited me to his house last Wednesday so I went and i stayed there a while. The next day at school he completely shunned me. I really understand, should i just keep a distance or conpletely destroy the friendship? Any advice or personal thoughts are greatly appreciated