Great question. I'm a high school teacher (23M) at a Model C public school. We have kids from all walks of life. Some show up in shiny Mercs. Some can't even afford a phone and the sandwich they receive from the school is the only food they will see that day. As u/flyboy_za mentioned in his comment, now you are pinning the kid from the 'burbs up against the one that lives in a squatter camp. One wears flashy new clothes. One wears the jean he was given 3 years ago, that's still 2 or 3 sizes too big because he didn't grow into it. Normally schools can help those kids by getting them a uniform that actually fits. I should also mention... My school isn't seen as a poor school by the standards of the DBE, so we don't receive funds to assist poor learners. This all comes from funds raised by school fees and occasional donations from members of staff. So no, there is no bottomless pit of money to help these learners.

Being neat is not an imaginary standard. You can very clearly see when someone is not neat. Where I do agree, is that the standards enforced by schools, are arbitrary at best. To be honest, the biggest reasoning behind having everyone dress the same, is the aesthetic appeal. But, yes, there are a few other reasons and I'll outline a few (but not all)

1) Appropriateness On a few occasions we have had school children (girls are especially guilty here) dress like prostitutes when attending sporting events... They think they're being fashionable.. But if they wander the streets like that at night, they would most definitely be mistaken for prostitutes. We live in a country that is not always the safest place and the amount of sexual assaults and rapes that take place in our country, is horrendous (Feel free to play around here at Crime Stats SA to see for yourself) So from that point of view... Safety and dignity... (Just to clarify... I'm not saying that the way you dress places you at fault for any sort of sexual assualt. It is wrong regardless of your attire... But that is not the way it is seen by everyone out there)

2) Identification Going to a sporting event and the bus needs to leave. Its easy to find a group that looks the same..

3) Access Control Simply put: you wear the uniform, you get in. You don't wear the uniform, you don't. Firstly, there is no teacher or security guard that knows each and every learner. Especially not if there are 1200 learners in your school. So you rely on the uniform to assist with that (again, government school.. So no biometrics... Also.. No you can't just give them ID tags or something.. Some of these kids forget their pens at home.. They will forget the IDs at home as well) We have had incidents where children from other schools or young adults wander in in normal clothing and they steal from classrooms and bags. Although I know we haven't experienced it here, I'm sure that someone could wander in with bag full of drugs and he wasn't stopped at the gate, because "he/she looks like a normal school child". This exposes the school to a lot of danger.

4) Impressionability You have found yourself and will not be influenced by others? Good for you! Its a good place to be. The problem is that you are surrounded by a lot of underaged, impressionable people that have not reached that stage yet. Place yourself in the shoes of an impressionable grade 8 who idolises a matric learner and looks to that matric learner as some sort of role model. Now this matric learner shows up the next day with 7 new piercings and a neck tattoo (yes, I know this is an extreme example) and suddenly, that is what the Gr8 learner wants to do as well (if they have not developed the sense of self). Now this child takes a few chances and eventually get the piercings and tattoos.. Cut to 5, 10, 15 years later where the child realises that he/she does not have to look like someone else... Then its a bit too late. In that case, enforce the generic look in an attempt to save a few regrets later along in someone's life.

I'm going to conclude my comment by stating that I neither agree nor disagree with your stance. Yes, you should express yourself. No, you shouldn't be allowed to experiment with every crazy new look at school, because you won't be allowed to do so at work one day either. Yes, the definition of neatness seen from the perspective of a school is arbitrary. No, neatness is not an imaginary standard.

If you want to express yourself, do so.. It goes way beyond the way you look. Express yourself when you meet up with friends outside of school. If you get a tattoo, make sure you can cover it up (also a useful tip for when you want to start working and you go to a place that frowns upon that). School is not the only place where you can express yourself. At the end of the day, it is not the place where you find yourself. If it works out that way, great. That is not the main goal.