Question about player killing in WoW?

Okay so I'm new to WoW, in fact I've never played. I am going to start soon. A guy at school swears he will kill me relentlessly until I give up and quit playing. Is this possible? I thought I had to agree to duel or flag myself for pvp. I just want to learn how to play in peace without all the crap. He is a pries t.