and one of the girls said she heard about it in elementary school from a principal that its in case you accidently bumped into a male cousin.
Brilliant. So now, not only did the principal totally make something up, but also gave over a message that you somehow need teshuva for accidentally bumping into your cousin. Nice.
In other news, when a rebbi teaches something wrong in the torah, you are supposed to stab them with a spear, as the gemara says in Baba Basra 21b http://hebrewbooks.org/shas.aspx?mesechta=23&daf=21b&format=pdf