Nah, thats too extreme. Go to the Principal and explain your situation. Figure out how to tackle the situation together. If they say they cant due to financial things to consider, accept it, and maybe you can raise funds at your local mosque or something. But if he is unreasonable and gives unreaonsable statements as to why he cant cater for your halal needs, then you can sign a petition. Signing petitions is the last resort, because they are kind of a serious statement.