I've already taught using a brilliant scale-teaching aid from Natalie Wickham: free pdf downloads of fingering diagrams for major and natural/harmonic minor scales. If you're using your laptop in the studio, just resize one of the diagrams so that the scale you're teaching fills the the screen, then put the laptop on top of the piano. That'll teach'em to learn F# minor harmonic with the right fingerings, once and for all.
Links to both sets:
Major scale fingering diagrams
Natural and harmonic minor fingering diagrams
I can hardly wait until Natalie creates a melodic minor fingering diagram set, which will require a system for notating several melodic minor scales (such as F# and C# minor) which use a different fingering ascending than descending in the right hand.
Update 4/13: Natalie has indeed created a chart for the melodic minor scales. You can find it here.
