I do like mixing subjects together as you propose. A couple things to watch out for though: It can lead to slowing down your learning of the main skill. For ex

I do like mixing subjects together as you propose. A couple things to watch out for though: It can lead to slowing down your learning of the main skill. For example, I might try to include TDD in any coding tutorial. While that's great, it slows down how fast the student can learn the new concept. Being forced to write essays that are X words long for your History report, turns most people into terrible writers who are unable to explain a concept in a fewer amount of words and are typically full of very long run-on sentences.