I think parents should tell their children what NOT to wear, there are some pieces of clothes that might be ok in a particular occasion (high heels or a sequined dress are fine if you are partying) but not in another (attending classes or work) and I am afraid that there some adolescents not being able to see these differences.
Anyway, as long as parents are paying for their children's clothes, they have the right to give their opinion.
In my opinion your parents should help guide you and help you to make your own decisions on what to wear.
If they need to tell you what to wear when you are an adult, then somewhere along the lines of raising you, they have failed!
My mother always told wear this