Jean Chall developed a theory of Stages of Reading after publishing the Carnegie Research Report in 1967 on the “Great Debate” examining research on whether reading should get taught through decoding or meaning making.
The theory, based heavily on Piaget's Stages of Development, concludes:
Reading development happens in stages
Reading is always problem solving
You move through stages in an environment
You can measure different stages of reading
Stages are successive, grow in complexity, and can stagnate