Model trains, WWII, Japan—any obsession or "limited" interest touches on geography, history, materials, technology, cause and effect, human actors, religion, engineering, art, languages, all kinds of stuff.
The best thing an unschooled child can have is a parent who realizes there is learning in everything. As to "resist," it can only happen in response to force or pressure, right? Parents should resist pressuring their kids, I think.
photo by Sandra Dodd