My kids learned about citing and plagiarism in history classes in high school - not in English where they didn’t write research papers. I don’t understand why if this is such a rampant problem in colleges they don’t teach this stuff. Most colleges do have some version of Freshman English or expository writing. Back when I was at Harvard they did some testing during freshman orientation - which seems to me an ideal time to go over the basics and steer students to the Writing Centers (which most schools also have) that can help kids who haven’t been exposed to this stuff in high school.