I’ve found myself in similar situations @religionteacher123, but the children I teach are younger and part of our parish, so their questions aren’t as… negative. Just curious to get some clarification, do you teach at a Catholic high school? Is your class specifically teaching the Catholic faith or different aspects of religion? And finally, is your school a diocesan school or an independent Catholic school?
But to echo what some others have said, you just have to know your faith the best you can so you can give them a firm witness. Honestly, you may be the only solid Catholic that they have interacted with! They may not have other examples in their lives to look to when they are seeking someone who is an active, practicing, and faithful Catholic. I’d research some of these hot button issues in depth to give a clear and cogent response, that way, like St. Peter said, you’re “always ready to give a defense”.
This wisdom is all over CA’s main website, but if one of the kid’s stumps you with a question, or you’re not sure how to answer it correctly, tell them you’ll get back to them the following day, or week. And then simply follow through. Those kids will appreciate that you took the time to give an answer to their question.
I’ve done this for 6th graders by always having a “Question Box” in the room where we do religious education. They can put questions in at any time on any topic. Of course, I encourage them to ask questions out loud, but this helps because then I can show them by answering that I considered their question. I don’t know if a similar angle would work with older kids, but at the very least, just prepare yourself to answer their questions. If they have really said such things that anyone who believes in Catholicism is brainwashed, then show them why they’re wrong. Do so over several days if you need to get through the curriculum. On that specific topic of brainwashing, here’s a good place where you can start answering them, and provide them with an alternative view that is different from their own:
Does Teaching Religion “Brainwash” Kids?