Dress codes are meant to make schools more inhabitable for children of all ages. Those who argue for their inclusion in school policy often argue that it makes going to school more beneficial for children, as they are able to have a stronger focus on the material that they're studying. In this context, it isn't viewed as a loss of individualism, but rather a focus on uniformity so there are not as many distractions within an educational context.
However, you'd be surprised at how seldom these results actually occur in real-life classroom situations. In fact, school uniforms can not only have detrimental results on the performance and expression of students, but it can also have more unsettling implications.
For example, one of the most common examples of dress code violation in modern times is when female students are told that their outfit is too distracting for the fellow boys, saying that they have to change or else face expulsion. This is often the case during warmer months, when a lot of students in the school are not wearing sweaters or other parts of a school's dress code that are more normal during the winter.
To understand why this is an issue is to understand how the question should be properly framed. In the aforementioned situation, the problem and solution are both placed on the girl. Though the potential for boys being "distracted" is part of the situation, it has no role in instigating the issue or solving it. The result of this is that all of the blame is placed on the female student, causing her to feel shame for her physique, something that might instill feelings of inadequacy and negativity.
This misdirection of blame is actually considered a form of victim-blaming by Shauna Pomerantz, a girlhood expert working at Brock University. Once you consider how rampant sexism is in our society in general, it makes sense that you wouldn't want your child to feel pressured in any way to feel the blame of that. The response that males have when looking at a female body is not a cause for the girl to revise her attire, but instead address why the male response is prioritized in that encounter. It should be noted that this is also an issue that happens at schools that don't have dedicated uniforms, making it a prominent issue of dress codes everywhere.
Another issue that is posed when you force students to wear particular uniforms is whether or not you're being fair to the culture of all of the children involved. For example, being able to afford a consistent wardrobe of uniforms for everyday use is definitely related to class, as some families are simply not wealthy enough to not afford to have one laundry day per week off. Some schools will often address this issue by having extra clothing for students who don't have a uniform that day to wear, but even the notion of somebody being chastised for something that they can't control gets into dicey territory.
For example, a lot of dress codes are based off of specific class-based assumptions about what is "proper". This is why you see dress codes so often shun designs of pants such as "sagging" ones, as they supposedly create an unproductive environment for students to learn from. However, this is a complicated issue when you factor in that certain aesthetics that are viewed as "not proper" are actually related to both race and class. For example, one could argue that a lot of what we associate as "improper" with regards to aesthetics are simply characteristics that we also associate with African-American culture. In a similar manner, many of the aspects included in dress codes (sweater vests, ties, certain types of hairstyles) almost always put white, Eurocentric traditions at the forefront, making them very exclusionary of all students who are attending the school.
Many people who are for dress codes think that they will provide uniformity among students, but it's always important to question what they mean for uniformity. Schools that often have dress codes ask students to not just wear the same types of clothing, but also wear "similar fits". This is how schools get away with saying that "saggy pants" aren't allowed, even if they're the same exact brand or model of pants as other students might be wearing.
For many, comfort and culture should take precedence over the tightness that they wear clothes. The argument that tightness plays a role in school clothing feels hypocritical, especially when considering what happens to girls who have shirts that are "too tight". Schools assume that by regulating the tightness and specific type of clothing students wear that they are creating equality, but that is not what equality looks like. Everybody's bodies are different and there are also overwhelming societal stereotypes of women that make it difficult for girls to feel comfortable in their clothing without feeling objectified or mistreated at school.
When you have dress codes intersecting with culture and then also have violations of said dress code result in academic consequences, you perpetuate a culture that puts many minorities at a disadvantage. For example, a 2018 study from the National Women's Law Center showed that 3 out of 4 dress codes at public schools in the Washington, D.C. area force schools to pull students out of classrooms for violating the dress code. This type of academic consequence has little to no regard for the well-being of students, as it places their academic success on how they dress.
When you factor in the previously mentioned ways in which certain dress code aesthetics can be associated with the intersection between class and race, it's clear that there are some groups of students that have serious potential to be affected on academic levels for clothing and cultural precedents.
The people who instate dress codes in schools aren't entirely wrong for thinking the way they do. For example, it's understandable that schools would want to figure out the best way to inspire and energize their students to learn. At the same time, it's also understandable that they would want to find ways to make the classroom less distracting. As the technological landscape of our world continues to evolve in ways that distract children from their studies, social media sites and other areas of entertainment prove more often than not to be more attractive to students, making them fall behind in their studies and not be as active in school.
However, the way to increase academic learning is to find a system that will work for all students, not just some. This is why school uniforms are ultimately unproductive, as they not only are ineffective at tackling the issue, but they also often discriminate and prevent certain groups of students from excelling at the school, possibly setting them on a course for the rest of their life.