Balancing piano students' scope and sequence is essential to a well-rounded musician. Of course, the first step is hand position, note-reading, and identifying rhythms. With young students, much can be learned by rote (copy-cat exercises with the teacher). By 8 or 9, note-reading is primary for the student to sense advancement. Most piano methods out there will do this: Alfred, Bastien, John Thompson are my favorites.
The second step is to develop techniques. Learning scales in 5-finger patterns, octaves, then double octaves, first major and then minor. Hanon and Czerny I have used. Hanon is geared for younger ones. These can also be taught by rote. Either way, memorization to disconnect the student from paper and connect them to what their fingers and hands are doing is key.
The third step, done at the same time as technique, is applying that technique to actual repertoire. There are many compositions which are simple: Bach, Mozart, and Beethovan, so dumbed-down versions are not really needed. The method books can also suggest works which correspond with playing level. Don't be afraid to choose works which stretch young players. Remember that they can be taught by rote, demonstration, or through theory analysation of chords.
Theory is the final aspect of piano. I like to incorporate theory within the actual pieces the students work on: scales, chords, intervals, rhythms identification, as we go along. For courses, I recommend Practical Theory Complete by Sandy Feldstein. Understanding the underpinings of the compositions makes students better musicians, sight-readers and performers.
Balance means that all aspects above are touched on in every single lesson. Finding repertoire that students may not otherwise choose (especially if they just want to play pop music) can be a challenge. Be sure to look for World Music, Popular Music, and choose from Baroque, Classical, and Romantic along with 20/21st Century composers. A fun tool for finding new repertoire for me, along with piano teacher forums, is Youtube!