No matter how you slice the education process, you're always going to have instruction and practice.
It seems Khan Academy has a great model for instruction and Code Academy has a great model for practice; it seems reasonable to posit that a combination of the two would be superior to either one on their own.
I would further posit that the blend between the two models of instruction and practice would be something that might be tailored to the learning style of each individual student. Some people learn well by understanding before doing, others by doing first then understanding.
Code School (i.e. Rails for Zombies) is a combination of the two! It's not quite what you're hoping for, though (it's always Instruction then Practice, rather than giving you the option to mix it up).
It seems Khan Academy has a great model for instruction and Code Academy has a great model for practice; it seems reasonable to posit that a combination of the two would be superior to either one on their own.
I would further posit that the blend between the two models of instruction and practice would be something that might be tailored to the learning style of each individual student. Some people learn well by understanding before doing, others by doing first then understanding.