“A good book for teaching”
Robert Cavally was one of the foremost flute teachers of the last century and on his death in 1994 he left 30 years worth of handwritten teaching notes to his student Bootsie Mayfield for her to publish after his death. The result is 6 books, a primer and exercise book each on tone, scales and velocity. Each Primer is divided into lessons, and has a fingering chart, basic skills advice and some theory. The books are also in this format but the material is more advanced. Cavally's very personal teaching philosphy comes across quite clearly both through the editorial notes and the exercises themselves. This is a slightly different approach to building a flute technique, and if you investigate further you will be richly rewarded.
Difficulty level, roughly compared to ABRSM exam grades. 0 is beginner, 9 is advanced (beyond grade 8).