First of all, there is no need for schools to be too strict with hairstyles. Because many people will resist organizing such activities, it is difficult to carry out them, so there is no need to make such a provision.
Second, especially some girls like long hair, which is normal. Especially since they grew up with long hair. If they are asked to change this habit, it will definitely be difficult for them to adapt for some time.
Thirdly, as boys, they can be asked to cut their hair short because they are used to it. Moreover, short hair is better for them personally and more conducive to their care.
Finally, it is more reasonable to stipulate that schools or students cannot dye their hair. Because if you dye your hair, it is easy to form a psychological comparison. Especially as a student, dyeing hair is not good for hair growth. I never dyed my hair when I was a student. And I often cut my hair short when I was at school. But for girls, every school doesn't stipulate that hair must be cut short.