You can read a bit about it here [1]. They structure reading around 5 pillars, phonemic awareness, phonics, vocabulary, fluency, and comprehension which is an evidence based approach[2]. Then if by the end of 3rd grade a student isn't reading at grade level they hold the student back to give them more time to learn to read so that they will be prepared for the more advanced material in 4th grade. I don't know as much about the math instruction.