In cases in which principals have failed to improve reading instruction it is because they have not fully accepted their role as school instructional leaders, because they don't see reading as a priority goal, because they don't understand what is involved in change, or because they view materials and systems rather than teaching as the key to the reading process.
Trubowitz, S. (1978). The Principal Helps Improve Reading Instruction. Reading Horizons, 18 (3). Retrieved from http://scholarworks.wmich.edu/reading_horizons/vol18/iss3/5