Everyone gives away, with almost everything they do, how well brought up they are - it is almost impossible not to write the quality of your upbringing in huge neon letters with everything you do. Very few people could identfy exactly what it looks like, but everyone recognises it.
I understand how peers with wide parental license look like a much better model of behaviour from where you sit. Many girls at 16 have been brought up by parents who don't actually mind what their daughters look like, or how they are percieved.
Are they trash?
Your parents may suspect that they are. It doesn't matter what they think. What do you think. Do you want to be thought of as being like them?
It sounds like your parents have put some thought and energy into your upbringing. Until you develop sound judgement (until you make the sort of decisions they would make), they will exercise what they see as sound judgement on your bahalf.
Tee-shirts are fine. Are you sure you are talkiing about normal Tee-shirts? Is anything written on them? Do these tee-shirts have messages? Do they suggest sexual availability /promiscuity? Do your tops reveal flesh around your midrift? If so, your parents think these all suggest poor judgement.
Jeans are fine. Jeans revealing where your cheeks part company, frames with a thong (fashionable jeans) also suggest poor judgement.
You sound like a smart, intelligent, woman with a strong positive self-esteem, and not desperate for any attention from anyone.
Until you can dress like it, rather than a fashion victim wannabe, aping the next generation of single Mums you envy for their sartorial freedom, your parents will dress you like you were Amish Barbie.
I wanted to offer you my insight into your parents point of view and motives; I am truly sorry to relate things you may not want to hear.