The whole age thing really doesn't matter. I'm 19 and in my class, I hang with a group with four other people who are aged 18, 19, 21, 25. There's also a lady who is in her mid fifties but we all get along with her just fine.
Uni and college aren't like high school, there's none of this immature nonsense where people assess you based on your age/looks.
Also, the age range will vary from course to course. My partner is doing a construction course at college and everyone is under 21 but I'm doing marketing and as you can tell from what I've said, the age range is massive (17 - 55)
Don't worry about it!