I'll just try to take on as many things as I can about the matter. LOCATION/OCCASION: "It's not Miss World/a Beauty Pageant, It's school".
(A student goes for school to learn.
A teacher goes to school to teach. )
Why should the teacher be able to wear makeup but the student can't? Because she's an adult?
You're implying with this age-based logic that all girls under the age of 18 can't wear makeup *anywhere* even outside of school. And since when was it illegal for girl under the age of 18 to wear makeup?
There was never the implication that school was a beauty pageant. A girl wears makeup according to her own personal style, Not to compete with other girls to see whose makeup is the thickest. The point of wearing makeup is to make *yourself* prettier.
Whether the girl uses her own money or her parents money is strictly between her and her parents. Though I agree that don't agree with a girl forcing money out of her parents just to buy makeup, You can't actually say this applies to every case of every girl who wears makeup. There are also a lot of girls who use their own pocket money to buy their own makeup. And not everything on their vanity has to be luxury makeup brands, Drugstore makeup is cheap and just as good as the ones in Sephora, Sometimes even better!
Some girls wear make-up to look prettier, Others to boost their confidence, There are even those who wear make-up just for fun. If it makes them feel prettier and more confident, Isn't that a good thing? If it makes the girl feel horrible about herself, Like she's ugly and she needs it, She could always take it off. No-one is forcing her to wear it. It's her choice and hers alone.
There is also the lipstick effect. The study that found that female students who wear makeup have higher self esteem and grades. It's really all about mentality.
Of course, There is the risk of break-outs and skin damage, But it that really your concern? If the girl thinks that make-up is ruining her skin, She'll know how and when to take it off and put away the brushes.
Of course, For students, The point of going to school is to study, But let's get real here. You can't give an idiot a piece of chalk and tell them to solve Riemann's Hypothesis. It really depends on the girl. Even if you take away her makeup, Can you really say that she's automatically just going to graduate as valedictorian? A girl, With or without makeup, Who takes her studies seriously will prove herself in her results.