You are also responsible for your own speech. And that includes what you actually say, not only what you intended to say. When the two don't line up, and problems are caused by that, it is incumbent upon adults to recognize that they misspoke, apologize for confusion, and clarify. If these kids were misconstrued, then an apology is in order, and a clarification needed. If that's not forthcoming, then the reasonable position is that they did indeed intend the message that was recieved. Not a good option for a school community wherein the populace is constrained to a fixed, young age group. And that is why your normal free speech rights do not entirely hold in the context of students at school - administrators are granted considerable latitude to deal with behavior that disrupts the school environment, for the reason that everyone also has a right to recieve their education in a safe, productive environment. Ignoring the trolls and waiting for them to grow up doesn't work when it comes to keeping high school kids in line - they'll have long since graduated and moved away before they grow up.