Stoned Kindergarteners?

Some time ago, a professor made an aside, mid-lecture, about "high kindergarten." She lived in California at the time this alleged phenomenon existed, which was in the sixties or seventies, but she said these were kindergartens where the kids were encouraged to get high. I imagine the pot was baked into something palatable to a child.

I'm presently making notes for a story inspired by this idea, but I can find nothing about it on Google. So, all you REALLY OLD folks who might recall that era, do you remember this? Did this really happen? Can you give me details?