You'll hear a lot of foolishness on the internet about high-rep squats. Most of it is along the lines of "OH, That high-rep squatting stuff is for the birds! No one trains that way anymore - it's just old-school macho B.S.!", or the opposite of that "High-rep squats are the only way to display your manhood!" Errrr, okay...
Look, if someone tells you that high-rep squatting might not be the only way to make good muscle gains in a relatively short amount of time AND they have a more moderate and intelligent plan for doing so, then they are probably worth a listen. If on the other hand, their first reaction is over the top, claiming that the only thing high-rep squats are good for are injuries or overtraining, then you need to get away from them - they have no idea what they are talking about.
There are legitimate criticisms of high-rep squats, but "not working" (as far as muscle growth is concerned) is NOT one of them.
From: Super Squats: How to gain 30 pounds of muscle in 6 weeks by Randall J. Strossen, Ph.D.
The Abbreviated Program
If you have problems gaining weight on the basic program, try this:
Bench Press 2 x 12
Parallel Squat 1 x 20
Rader chest pull 1 x 20
Bent over rowing 2 x 15
This program has worked some absolute miracles on people whose bodies defied development on countless other exercise programs, and these three exercises - the bench press, squat, and bent-over rowing - are Peary Rader's precise recommendation for "great results, both in the legs and the upper body" (Rader, 1964, p. 25). Just remember to work absolutely as hard as you possibly can on these exercises: Fight for every last rep and try to add weight to the benches and rows every workout, exactly as in the squats.