I know you're in high school now and you know just about everything. But when it comes to Mark, trust me, your parents are right. They might not handle it perfectly (in time you will learn that no parent is perfect), but please listen to them.
Mark seems like a nice young man, and in some ways he is. He says he loves you, and he might. But don't think you can change his dangerous side: he doesn't love you enough to change. (Read that sentence again.)
Here is the truth: He says he will be faithful; he won't. He says he'll stop using drugs; he won't. He is going to take you places, literally and metaphorically, that you will regret later. And in the end he's going to break your heart.
I promise you that another young man will soon come along. In fact, you know him already. This one is truly sweet, but he is still not the man the Lord has chosen for you. Be patient! Learn to "Be still," and you will save yourself a lot of heartache.
I'm linking up to the Faith Barista Jam: