You're full of it.
The school can prevent me or anyone else (including students) from assembling or associating on school grounds anytime they want. Happens all the time. Try to get into your local principal's office on a Sunday. You won't be able to even if he or she is there working and has his kids playing in the gym. That is not a 1st amendment violation; it is ordinary selectivity of entrance. Also, try to get you and your drinking buddies into the judge's chambers to "associate".
Your statement is so painfully ignorant of established precedent, you're embarrassing yourself.
Read the decision. The Reagan appointed judge didn't agree with your assessment - thankfully.