Students should feel comfortable and wear what they want in school. Choking tie, tucked in shirt, pants with belt and formal shoes isn't the right clothing to school. If school wants dress code, it shouldn't require formal clothing. It should require clean t-shirt with jeans or shorts and house shoes.
In particular gentlemen, we should be dressing students in business style clothing to get them ready for the world of work. A tie should be properly worn, shirt tucked into the trousers and smart, formal shoes. Students should look smart in school, as you need to in the workplace, in order to prepare them.