How do i stop picking the wrong guys to be close too?

last year i was good friends with this guy and everything was going well,until he got expelled b/c he got too many detentions and all the teachers hated him and he told me the day of and it was like one giant smack in the face but now hes a druggie and hes just a really bad kid..... and then this year a totally different guy came and him i and became so close we were like brother and sister and i thought i made a right choice by trusting him but he got expelled 2 days ago because of some really inappropriate things he said to girls and the reason he came to my school is because he got expelled from his old school and i didnt know why but it turns out he did it with some girl and he never told me and i trusted him........we're only in 8th grade by the way and he lied to me saying he never did it,i just feel so betrayed and used and discusted....now the whole school is like talking about it and i skipped school yesterday so i wouldn't have to deal with this crap.idk what to do...help?