"I'd raise a well-threaded eyebrow at that. I wouldn't automatically assume anything untoward, but I'd assume that they were spending too much time on grooming and possibly being groomed by adults, and not enough time on homework and pets. "
I did not misunderstand you at all, Limitedperiod, and I rarely misunderstand other posters either (and what a rude comment that was).
Unless by spending too much time on grooming and possibly being groomed by adults, and not enough time on homework you mean something completely at odds with what those words mean and what they imply -- what they mean and what they imply is that those girls are choosing vanity over homework and other activities of substance, or someone has an untoward influence over them.
You should not assume a girl who wears makeup is not spending enough time on homework. To assume that is to judge her based on her appearance. Judging women based on their appearance is what yobs on building sites do. It arises from misogyny.
If a teenager was so good at her make up and dress sense that she looked sophisticated beyond her years, then I would wonder at that. I wouldn't think badly of her, but I'd wonder who was teaching her, for what motives and to what detriment of her school career and values.
Do you understand?
(condescension duly noted 
)
What I understand is that you are unable to see past looks when it comes to teenage girls.
If they look like children then they are fine in your books, and you assume they are probably studious and with decent values. If they wear badly applied makeup they look like 'clowns' and have some sort of issue as far as their studies and their values go. If they manage to look good in their makeup then according to you there are some nefarious forces operating in their lives -- either someone is forcing them like greenhouse plants into precocious adulthood, or they have had to sacrifice values or academic performance in order to learn how to choose the right foundation and powder and apply it properly.
Makeup is not rocket science. Some teenagers have a great visual sense and quickly learn to choose the right product in the right shade and to use it really well, and with no need for the protection of their families 
for the learning period.
Don't judge others or make assumptions about them and the people around them according to your own problems doing this, or assume it's as hard for everyone else as it was for you to acquire taste and the really quite minimal amount of skill it takes to apply a little carefully chosen slap.
You seem to have some sort of issue with the fact that teenage girls are moving into adulthood. They are not in fact children at age 14, 15, or 16. Most are capable of bearing babies by the time they hit 14. I think you need to examine why you believe they are still children, and why teenagers looking like something other than the children they once were but are no more (wearing good quality makeup) makes you 'shudder'.
I think you should also examine why you think expressing consciousness of their appearance means teenage girls have lost track of academic focus or 'values'. Girls can be both 'sophisticated looking' and very intelligent and high achievers, and they can and do choose to look as 'sophisticated' as they want to, with or without any input from others. There is no inherent contradiction between looking like a model and being intelligent and focused on your academic performance and being a decent human being.
Teenage girls can't win, can they? -- wearing trowelled on orange makeup makes them 'clowns'. Wearing makeup well makes them some sort of 'older-than-their-years sophisticates'.
They should not focus on their own appearance. That is the prerogative of judgey adults.
They should not notice the appearance of others or make anything of it. Humiliation of girls based on appearance is another adult perk.