Billy Mummy was in Lost In Space, and did a few Twilight Zones. He was one of those very popular child actors who never found a niche as an adult actor. I think he’s still involved in various charity works.
Bless the Beasts and the Children
A hippie movie approaching Billy Jack with hamfisted polemics against injustice to kids at camp and of course buffalos
Mummy was in it
He got in trouble a bit then for weed mostly I think
Scandalous back then