This describes like 80% of people who graduate from public high school. I think it's worth acknowledging that most people struggle with what a lot of us consider "the basics".

AMI only accepts trainee teachers who have already have a bachelors (as a minimum) and their pedagogy seems to be more rooted in experimental results than simply psychological theories (see e.g. Angeline Lillard's book for further details http://www.montessori-science.org/montessori_science_genius.... )