I would never teach that easy finger[non musical] system...If you have an arranger student..still teach proper chording..When I taught students[arranger students], I used the Pointer system[books]..The ideal was based on third inversion chords..but made simple by using your pointing figure to the root of a chord , you thumb two steps to the right and your pinky three steps to the left,,As in the C maj chord..Pointer to the C, Thumb to the E, and pinky to the G...

Then no matter what board they advance to ..they have basic chord structure..They can also be taught piano play with out the false chording [one finger]..They will adapt to proper teaching of the piano..