Help my son express his freedom of speech

Hi! My name is Allen and my son is trying to make a stand at his school for the right to fly the american flag on his truck. His school has told him and his friends that they are not allowed to fly their American flags. If they do not comply they will face consequences. They gave them 3 choices 1 take the flag down, 2 leave school, or 3 have their parking pass which they paid $30 dollars for revoked. So if you could we are trying to raise money to help him and his friends wrap them with vinyl with the american flagif you can help that would be great if you can't afford it please share this thank you for taking the time to read this.