School officials may not advance or endorse any particular religion or sect, and may not prefer religion to non-religion.
Teachers may teach about religion in appropriate academic settings, such as history class, but may not reach from a sectarian ‘perspective’ or endorse a particular belief system.
Students have the right to maintain their own religious beliefs. They may not be pressured to participate in any religious activity, or in activities which violate their beliefs. School officials should try to accommodate reasonable requests for the private expression of religious beliefs. (ACLU, 1).
This briefing paper is inaccurate. Religious aspects can be part of school activites as long as the school doesn't promote one religion over another, or make the religious aspects mandatory.
One of the few good things Clinton did was stand up for students religious rights at school. He set federal guidelines that laid out student's religious rights (he didn't break any new ground, he just restated the rights the courts have long recognized.) I believe it contained the phrase "schools should not be religion free zones".
The ACLU briefing paper has been widely held as inaccurate. It was designed to confuse school administrators and have a chilling effect on them.
The ACLU does do some good stuff, but when it comes to some subjects (like religion in school) they lose all legal sense. They are against it, and will twist, lie, and cheat to stop it in any form. Whether it is contitutional or not.