How long will it take to gain muscle?

I am 13, a freshman, 5 foot 7 and I weigh 135. I am sort of muscular. I was wondering how long it will take to gain a good amount of muscle. I work out 3 times a week at my high school's gym and lift weights, do pull ups, push ups, and other things sometimes when i dont go work out. I also drink protein after i workout (it's a certain kind of whey that was recommended that people under 16 to use).