Sorry, but just because you are no longer a minor in your states eyes, that does not mean that you can do anything that the law allows. Our society is made of laws and rules that we all must adhere to, even when we may not want to. Additionally, 'society' has allowed for certain 'exceptions' to the statutory rights, for the good of the rest of us. An example would be that you have the Constitutional right of free speech, but you can't holler "FIRE' in a movie theater.
Additionally, your employer may have certain 'provisions of employment' which you feel violate your rights, but you 'waive' those when you elect to work there. Again using the free speech as an example, you will probably find yourself unemployed if you exercise that right by 'cussing out' your employer or supervisor.
Same with your school. They have certain policies and rules that are 'for the common good' and you may feel that they might enfringe on your rights. (An example would be if your state allows you to drink alcohol at eighteen, but you still couldn't do so on campus.) That is why most schools have published policies and rules in place. Also, why most of the schools now require you to sign a 'contract' accepting those rules at the start of each school year. If your schools 'policy' is that a 'dismissal pass' must be signed by your parents, that is a 'reasonable requirement' and you have 'no statutory rights' to challenge it.
