From season 1 of The Secrets of Isis:
In "The Show-Off", an arrogant student learns a lesson in humility the hard way. First, Isis (Joanna Cameron) rescues him after his ladder breaks. Later, on a Science Club trip, he and some of his classmates, along with teacher Rick Mason (Brian Cutler), are trapped in a cave with an escaped gorilla.
The episode was directed by Arnold Laven, which reunited Laven with one of his former charges at Four Star, producer Arthur H. Nadel. The two previously worked together on The Rifleman years earlier. What I'm not sure of is if it's either Bob Burns (Ghost Busters) or someone like Janos Prohaska (ex-The Andy Williams Show) as the gorilla.