Harry Potter Series Question?

The five boys are the only five Gryffindor boys in Harry's year, as evidenced by their being the only 5 boys in their year's dorms. We can't know for sure how many girls there is because we haven't ever seen the girls dorms. I would think there aren't others, because they've never been mentioned, and JKR doesn't usually have a problem with mentioning minor characters, as there is at least 200 characters that are mentioned at least 12 times throughout the series.