Can I sue the school, principal, church for libel?

With respect to the school's actions, your question is focused on whether you have a cause of action for its failure to renew your contract and or for libel/slander. With respect to the contract, one would need to review the contract; however, since it sounds like the contract was up of renewal, then school has practically an unfettered right to renew or not to renew. Moreover, in all likelihood, you were an at-will employee under that contract, which would allow the school to hire or fire for good cause or no cause. With respect to libel or slander against the school, it is not clear whether the school made any communications, rather the communications appear to be from parents or kids. Accordingly, the school could not be held responsible for defamation for comment made my parents of students. With respect to an action for defamation (i.e. libel/slander) against the parents, you would need to show that the parents comments were not true, they were defamatory and that they caused you damage. Since your summary did not indicate what specific comments were made, it is difficult to determine the merits. Furthermore, since the parents may be expressing an opinion and it may be difficult to prove proximate damages, the merits of your contention are more speculative. As a practical matter, it may not be a good choice to sue parents and/ or students for defamation under the circumstances you described as it would tend to bring these issues out in the open which may impair your ability to secure new employment.