|the "involuntary public figure"|
You can speak freely, but if you make false statements that damage another person's reputation, that person can sue you for defamation. If you are sued, you're more likely to prevail if the person suing you is considered a public figure -- for example, a celebrity, sports figure, politician, or a public official or someone involuntarily placed in the public spotlight (someone accused of a high profile crime). That's because a public figure would have to show that you published your statements with "actual malice" -- that is, you knew the information was false and you published it anyway. Public figures are held to a higher standard because they are expected to have thicker skins.
Are school employees public figures? Courts in a few states -- Arizona, Connecticut, Illinois, Kansas -- have ruled that teachers are public figures (public officials); and a few states have ruled that they are not -- California, Florida, Texas, Maine, and Virginia. Some lawyers contend that the teacher should be considered a private figure unless serving in an official capacity such as a principal or school superintendent; others have argued that teachers should be classified as public officials.
When newspapers publish stories of teacher misdeeds ... they're typically repeating criminal allegations. In other words, they're reproducing charges that are a matter of public record (and at the same time, the arrest may make the teacher an "involuntary public figure.") If a newspaper reports on a teacher's misdeed that is not yet a criminal charge, the newspaper usually has sufficient evidence to prove the truth, an absolute defense to defamation. That's fine for newspapers with the funds (and insurance) to defend these battles. But no matter what rights you may have, the expenses and risks of defamation claims are serious enough that you may want to reevaluate your reporting.
P.S. Dept. Besides defamation, you may also want to consider whether your disclosures could trigger an invasion of privacy lawsuit.