Wild mix of 60s TV icons
Believe it or not, 1961, the most familiar face in this film probably would have been Billy Gray, from the long-running series FATHER KNOWS BEST. Both he and Lee Kinsolving (the two male leads) were 23 when this film came out: a little long in the tooth to be playing teenagers.
But look at the list of other (later) shows represented:
STAR TREK - William Shatner
GET SMART - Ed Platt
BATMAN - Stafford Repp (playing a cop as usual)
Not to mention the ubiquitous character actor Vito Scotti, a very young Beau Bridges, and Marlon Brando's older sister. And of course Patty McCormack who hit it big on TV a little later than some of the others.