I've heard some say that high reps are useless for building any kind of strength (even endurance-strength),
Some say also that anything over let's say 35 reps or 50 reps is useless to build muscles. That's false, even with high reps and light weights we can become really strong and gain lots of strenght for speed, explosivity, endurance and even sheer strenght. Of course it's not building big muscles. It's small muscles but really powerful and with lots of potential.
There was a Indian wrestler called Gamma (or something like that) who was doing about 4 000 reps of special indian style bodyweight squats every morning plus thousands of reps of other bodyweight exercices each morning. I didn't see any picture but I've read he had very impressive quads.
My brother built some serious muscles while training for kung-fu classes, just by doing hi-reps, never heavier than 5lb dumbells except for some squats with an olympic bar but I think only 30lb, everyday routine, always fast movements, exercices like 150 reps press chest with 5lb dumbells, shadowboxing with weights, etc...
"Do your best, don't worry, be happy" - Meher Baba