The 2009 remake does a better job at bringing its story to life, but 1975's 'Escape to Witch Mountain' is still a good film.
The cast are all fine in their respective roles, even if none of them particularly standout. Eddie Albert (Jason), Kim Richards (Tia) and Ike Eisenmann (Tony) are satisfactory, as is Donald Pleasence as Deranian. With that said, I think Pleasence should've been the main villain here - there's really not much need for Ray Milland (Aristotle). Disney had a knack of doing that sorta thing in these early eras, having a bad guy and a bad guy's sidekick - most of the time, just one would suffice.
The pace of the film isn't perfect, but the premise itself is intriguing enough to keep it chugging along at a suitable rate. More action-packed events would've been greater, especially as the opening titles seem to suggest that that may be on the horizon.
That wasn't the case, yet I still had a decent time with this.