dunno what name: You don’t need to teach other religions. It just involves teaching ours from a standpoint of how missionaries take things out of context. It means teaching NACH better. Most Yeshiva guys learn Novi in bits and pieces through Gemmorah. That’s not enough.
I have found that people who learn these things get stronger in their Yiddishkeit. Also, when they are accosted in the street, they’ll know how to handle it. Missionaries go through Jewish neighborhoods all the time. They don’t bring up their own nonsense. They misuse TANACH to make their points. Knowing these things will also help in protecting others from this evil.
A 15 or 16 year old is certainly old enough to understand and experiences the bombardment of xtion holidays. You can’t shelter everyone 100%.