Torah
“Why they did not teach that you can’t bring non-kosher food to a Jewish person in HS, in between Hilchos Shabbos, Tznius, and basar v’chalav, I do not know.”
Bimchilas kevodecha, in Yeshiva highschool and elementary (im a boy) they taught us numerous times that on Shabbos one should be careful when crossing to always cross when its your light because if not you may cause a not (yet) frum Jew to have to stop for you and then when he accelerates again he is mechallel shabbos because of you. Im sure you heard this in school as a kid, and you should have been able to extrapolate that all “lifnei iver (lo sitein michshol) is assur.
Dont blame your school that you missed the boat. No offense I know its harsh please forgive me.