Parents don't like my X

I'm 17, senior in high school. Recently my X and I have reconnected and we really want to date again. My parents don't like him because of some of the things he's done in the past but he is a different person this time so I really want him to sit with my parents and talk it out. And he's willing too. Just I'm scared how it'll go down. What if they don't allow us to? Or have such strict rules with it that's it's basically impossible to hangout? Also should I wait there when my parents are talking to him or leave the room?  I just don't want to go behind my parents back anymore