The silencing of Christian and Right-wing voices.
We have a local case where a 13 year old student was protesting abortion and was made to stop. He was following school rules to a T (protests and stances are allowed during non-classroom time and must not be disruptive or explicit). His mother even called the school ahead of time to let them know he was doing this. They gave no opposition at the time of the call. He wore a T-shirt stating abortion facts, passed out pamphlets that listed what happens during the stages of development of a fetus, and more abortion facts. He also wore tape over his mouth to symbolize how we've silenced so many voices that never had a chance to speak. The student was seized, made to turn his t-shirt inside out, told to stop his activism and the student body was told to throw away the pamphlets and not read them. It is fairly obvious that he was targeted for his beliefs because other similar activisims were allowed (gay rights, diversity, etc).
The Alliance Defense Fund spoke on the radio about how some schools are even teaming up with certain political and social groups (he used the example of one school supporting gay rights). These groups come in and pass out literature, have seminars, and encourage students to be activists within the schools. However, students who oppose peacefully (the example was a student who wore t-shirt expressing his views that homosexuality is an abomination in the eyes of God) are silenced.