Avira, thanks for answering my question and sorry for the scolding you are getting…
I see that you are somewhat in a pickle: you proclaim and teach importance of the truth but then have to say things to your students that are appropriate for the school. I don’t think it is wrong per se, just an intellectual contradiction that I am sure you have a resolution for. It does not look like you are doing it just for financial reasons also.
What I am not sure though whether your declared behavior is always what actually happens. As others mentioned saying, for selected ones, that some Jews are cut off, even if they can come back in not what a serious, non-LW, MO Rav would say .. so, it is probably similar with many other issues that you may not even notice consciously. Also, with sending kids to “frummer” places – I hope this is with agreement of the parents and your school administration. This might be a geneva otherwise.
JJ Herman sent a kid to a yeshiva and then went to tell his parents. I think we would have been arrested in our days.
So, back to putting myself into the shoes of the parents – I presume my kids are serious enough to hear the “truth” for you and I would probably inform the administration when I find out that teaching is not as expected from the school. And I would when kids start calling their cousins not part of am isroel or something like that. In the ideal world, I would also go to beis din to recover tuition and bitul zman.