Discrimination by the back door

http://news.bbc.co.uk/1/hi/world/americas/8563122.stm

If laws forbid a school from discriminating, but not private citizens, then clearly one should just hand over the task to the citizens, rather than question whether discriminating is a good thing.
After all, if it were good, surely the country would want schools to promote it?
Or perhaps the governors think that the school rules are silly, in which case I wonder why they're governors, their job being to ensure that the rules are followed.
A private party will not cater to students' best interests because it will exclude some, thereby detracting from school life, and not have the advantage of using school facilities, which are probably designed for the right number of schoolchildren and are well located for all attendees.