Well I'm a 15 year old girl and I find that many girls my age tend to wear too much make up, especially when I went to an all girls school. Even though there were rules stating no-make up, many girls would wear black eye liner and mascara (making them look like as if they had a hangover IMO), as well as heaps of blush which gave them an 'artificial' look, kind of like over-doing it in Photoshop. Now that I'm at a co-ed school, I find the girls there don't put on as much make up as the ones at an all girls school.
As for me, I only apply a light amount of make up on for special events such as weddings, birthdays and school photos. I find that I look the same with make up on as I do without.