Making up for using light weights?

I'm doing an arm workout at home with two 10 lb. dumbbells. I'm 14, 5'7'', and 126 lb. I'm trying to gain strength and weight for basketball, many of my school's older players are obviously stronger and bigger than me, I have trouble guarding them. I'm confident enough to try and challenge them. I'm starting to squeeze my way into weights, a lot of my growth has already gone on. Many sites i've searched have told me just to do more reps with light weights as opposed to heavier weights with low reps. However I truly believe this only makes the muscle more adapt to going for longer periods of time; increasing muscle ENDURANCE not strength. How can I make up for this?