To me, realistic RPing is usually just doing what any normal student would do on a day-to-day basis. All the students in the books were totally normal; there wasn't sombody who sang all day, had extra powers, etc. Also, something that is well taken care of here: the amount of Werewolves/Animagus/Metamorphmagus. Not everybody in the wizarding world can change their appearance without assistance from a wand. Not everybody can be an Animagus - especially not first-years.
Which brings me to my next point: first-years. I don't like that first-years have full-on relationships. I know that eleven-year-olds usually have just a few little crushes. They blush when their crush speaks to them, things like that. Nobody ever thought about kissing when they were eleven, except for maybe a very awkward peck on the cheek. I know that one character (I won't name names) had about three or four girlfriends in his first year. To me, that is very unrealistic RPing.