how do I persuade my parents into letting me sleep over at my boyfriends house
It's probably not happening, because parents remember what ALL young guys are interested in. (Your Dad was one and your Mom dated them.)
Start having your boyfriend come over to your house to study (door open or in a common area) or play a game or something. Parents want meet and know a young man who is going to be part of their daughter's life. If they find him trustworthy, you will have an easier time all around. (And if they do NOT find him trustworthy, maybe they see something that you are ignoring. Maybe??)
Take care, and
Chances are, that no matter what you do or say to your parents, they will never let you. parents will be parents, they will always want you to be safe, and probabaly wouldnt let you stay at a boys house. considering what could happen...surrre "we wont do anything" but they dont know that for sure. they will always expect you to be innocent, and young, and not old enough to make your own decisions. thats just how they are.
Simple answer: you don't.
If you're young enough to actually need your parent's permission, then you're too young to be sleeping at a guy's house.