For the Beginner:

 

Bastien Piano Basics  by James and Jane Smisor Bastien, Neil A. Kjos Music Company, San Diego, CA.

Levels include:  Primer, Level 1, Level 2, Level 3, Level 4.
Each level has four thin books including:  Piano, Theory, Performance, Technique.

 

Students studying Bastien Piano Basics levels 1 & 2, also learn pieces from:

Bach - Schaum for Piano Book One (based on events and episodes of Bach's life), Belwin Rockville Centre, Long Island, NY.

 

Students studying Bastien Piano Basics levels 3 & 4, also learn pieces from:

From Bach To Bartok Original Piano Pieces By The Masters, Vol.C, selected & edited by Denes Agay; Warner Bros. Publications Inc., New York, NY.

 

For the Intermediate:

J.S.Bach Two-Part Inventions for the Keyboard, edited by Willard A. Palmer; Alfred Publishing Co., Inc., Sherman Oaks, CA.

Béla Bartók 5 Mikrokosmos; Boosey & Hawkes, New York,  NY.

Standard Piano Classics 24 Masterpieces In Their Original Form; Practical Performance Edition by Allan Small; Alfred Publishing Co.,Inc. Van Nuys, CA.