Francoisadt: What did you mean by 'middle yellow block'? There are only two.
Also, Dollopuss: I've made it to Level 6 a few times, but I think most of that was chance. In order to perfect the Spring Stage, do I need to get to a point where my eyes concentrate on the springs, and not Mario?
He means the yellow top of the elevator in the center of the screen.
Overtime, you will build muscle memory when moving Mario to the right and up the ladder while looking at the springs appearing from the left. However, some people are able to use their peripheral vision to see where the spring lands while watching Mario. There's no single fool proof way other than practice practice practice, but my video should give a good starting point on what to concentrate on.