Teaching Teaching

Over the last three years, my older sons have gone from near-zero knowledge of Spanish to fluency.  Given my open disdain for foreign language education, whats the backstory?

I started them in 9th grade because almost all good colleges impose an admission requirement of 3-4 years of foreign language instruction.  From the outset, my boys planned to demonstrate their competence on the Spanish Language AP test.  Going through the motions would not suffice; we knew my sons actually had to learn...