This is a really difficult discussion, and i think that here never really a good answer for is, but it's interesting what others are thinking...

I think that playing a realistic first year is really difficult, most of the time is it just fun to play a really cute and small firsty, but the most difficult part about it is to NOT make them too childish.

Kids from 11 year are indeed not calling their parents mommy or daddy, they can do it when they are home or alone with their parents, but it's just not cool to do it when others are hearing it. My little brother is almost 8 year, and even HE calls my mom just 'mom' instead of mommy when he is playing with his friends from school.

But... even now that they are *trying* to act mature, they still are young and the whole world is new for them, especially Hogwarts, so i think that they can act excited, hyper or even shy, but not all the time.

It's normal that, if a first year has a pureblood family, he or she already knows something about the wizarding word, but it's just impossible that they know everything about this world. I also think that a 11 year old can't have a boy/girlfriend, maybe when they are 13, but not younger than that...

But what i like the most, about a first year, is that when you let them be a little shy or unsure about this whole new world, that they can grow, every year they can change and i like it to see how that happens!