teenagers are autonomous beings that own their own bodies and have 100% discretion to make their own decisions, whether their parents like it or not. and, the law has to uphold that autonomy and self-ownership - whether the teens are making a mistake or not.
further, the system is fundamentally correct to teach that gender is a social construct that we have the ability to transcend or reverse if we feel like it. arguing otherwise is backwards and ignorant.
maybe you got a tattoo or a piercing when you were 15 and regret it. you can tell me it's not the same thing, but it is the same thing, and the more you assert yourself over the teen, the more likely they are to rebel against you - and prove that they do own their own body and it is their autonomy that is paramount.