The school had every right to do what it did for a variety of reasons, the first amendment does not factor into it. First off, children do not have the normal cache of rights awarded to adults of sound mind under the bill of rights. They may not purchase firearms, for instance, nor is age considered a legitmate prejudice under the law, which is why stores can not only ban sale of cigs to minors but also items like matches and lighters, without suffering legal consequences, as they would if they refused to sell me one.

Further, the first amendment does not cover anyone's right not to be offended. You or I can walk up and down the street with T-shirts saying the most derogatory crap we want, there are very few restrictions most of which are never imposed, i.e. you can not incite to panic or riot by screaming a crowded theater is on fire when it isn't. These kids certainly did not violate anyone else's freedom of speech or religion, and were they adults, or were they not in a public school, it would be nigh impossible to take action on the matter.

You are certainly not violating anyone's rights by wearing t-shirts that decry their religion, there are any number of t-shirts sold which make snide or mocking comment about any number of creeds, religions, ethnicities, political affilitions or genders. Crude, tacky, ignorant, and 100% legal... as they absolutely should be.

Such restrictions as do exist were made for very specific reasons and are typically enforced as circumstance demands, they do not apply to minors, any more than spanking your child qualifies as assault or battery, as it would for an adult. Although I certainly agree the parents of these kids could use a good public flogging, they certainly did not violate any laws I am aware of, schools simply have additional leeway on certain matters for common sense reasons that have been upheld by SCOTUS many a time. So too, do businesses and workplaces have a right to enforce dress codes and moral restrictions - in the work place itself, and this too has nothing to do with anyone's failure to obey those restrictions actually violating someone else's rights.

Lastly, I have to take issue in this context with your remark "And churches wonder why less and less people want anything to do with them... " which is more than a tad ironic while decrying t-shirts calling a religion evil. You're criticizing all churches because one criticized a church, you just used nicer words. If the t-shirts had said "Islam is a religion with numerous faults that many of us feel inspire a disproportionate number of its followers to rash and wicked acts" it would have been much the same statement, just politer, like yours were.