There are many schools of thought on when to teach a young pitcher a breaking pitch. My personal opinion is that speed is taught first (by teaching great mechanics), control is taught second and movement is taught third. An 11 year old throwing 40 is not there yet. That being said, I am good with introducing spins as long as the pitcher understands that a pitch will not break until speed is 55+ and won't work well until upper 50's+. A pitcher does not have a drop just because the ball spins correctly.
I think you forgot to mention another key ingredient to creating movement: the rate of spin per second. To say that "a pitch will not break until speed is 55+" is a fallacy. Conversely, you could have an "upper 50s" pitch with very little spin and not much movement. High spin rate + speed = movement.