Students under about 6 can start with this:
Step by Step Piano Course - Book 1 (Step by Step (Hal Leonard)) (like this:http://www.amazon.com/Step-Piano-Course-Book-Leonard/dp/0877180369 )
These are the first two books for older beginners:
Schaum Notespeller - a workbook. (like this: http://www.amazon.com/Schaum-Note-Spellers-Method-Supplement/dp/0769234534 )
M. Aaron Lessons Book One - method book (http://www.amazon.com/Michael-
Belwin Piano Method Book One - method book (http://www.amazon.com/Belwin-Piano-Method-Book-Grade/dp/B003FQQ96K/ref=sr_1_2?ie=UTF8&qid=1380216784&sr=8-2&keywords=belwin+piano+method+1)
Add note flashcards.
After completing Book 2 of either method book, introduce:
Dozen a Day Book 1 - Technique / Finger agility (http://www.amazon.com/A-Dozen-Day-Book-1/dp/0877180318)
I generally introduce chord symbol and playing by ear around intermediate level note reading, since the reading takes the most discipline and sets a student solidly in a mindset of hard work. I demarcate intermediate level as my teacher did, with Bach's Minuet in G.