This is not legal advice. And should not be taken as such. Always consult with a lawyer or attorney before taking any legal action.
IN ANY OF THESE CASE CONTACT AN ATTORNEY OR THE EQUIVALENT IN YOUR COUNTRY AND SEE IF YOU HAVE A CASE!!!!
If you have created your own unblocked game site are are dealing with punishment from your schools administration. Look at this check list to make sure you have a case.
If you are being punished for bypassing security software. Then you most likely have no case against your school or school district.
If you are being punished for using the game site. Then you most likely have no case against the school or school district.
If you are being specifically punished for using your own site but other users of that same site are not being punished by school ADMINISTRATION. Then you may have a Selective Prosecution case.
Was the website created on school computers? (if no procedure)
Did the website make defamatory statements against administrators, teachers, or others? (if no procedure)
Is the website hosted or maintained in anyway by the school? (if no proceed)
Did the website threaten students, administrators, teachers, or others? (if not you may procedure)
If you said no to all of these you most likely have a 1st amendment violation case against your school or school district.
If you live in the US contact the ACLU or the EFF
If you live outside the United States contact an attorney (or the equivalent in your country) as most countries have similar laws that will protect your right to free expression and free speech.
For more information read this Guide from the EFF * (while this is directed towards student bloggers most information in here can still be used by students who host unblocked game sites and other things)