Part of our calling to shepherd our children (and the flock if you are a pastor) is the realization that false teachers can turn truth on its head. We inoculate children by warning them of this ability of those who would teach what is not true.
Just for fun, here is a proof that two equals one. Only of course two does not equal one. There is a hidden problem with this proof. See if you can find it. HT: Jeff Sylva, my kids science teacher.
a2 = ab
a2 – b2 = ab – b2
(a + b)(a – b) = b(a – b)
a + b = b
b + b = b
Hint: The problem is between step 4 and step 5.
Use it with your high school children to help illustrate why they need to talk things through with other caring adults. We all need shepherds to care for us.