My bf won't drop the thought of me spending the night?

First off, we're in high school, and he hadn't thought about it until one day a friend of ours said she told normally tells her parents she spending the night a girl's house but goes over to her boyfriend's instead. once hearing this, he started asking me if I could spend the night at his house. I told him I HIGHLY doubt it, bc you know the sex thing. He dropped it for a while but thanduring summer he brought it up again. I said it wouldn't happen and he dropped it. Than it was prom night and he asked again. we texted my dad telling him that we were supposed to see his grandma in the morning and I wanted to come with. dad simply said "I'll make sure u get up on time." than he brought it up a couple of times over summer being much more persistent, pointing out he's waited over a year. I said that's not the point, the point is my parents don't want me to get pregnant. he said he didn't get it bc it's not like sex would happen anyways.

Than a few months ago we went to a concert in a couple of towns away together and we didn't get home until 2 in the morning so I asked my dad again and he said that this was going to be the only time as long as I agreed to go to school at noon.

Now he keeps bring it up, saying "I want you to spend the night again." I pointed out that dad said this was the only time and we shouldn't push that luck. he still keeps asking and getting pissed at me saying I just don't want to and that's y I'm not asking.

What should I do? Why won't he just drop it?