Given the education teachers have, it's not their fault. Teaching is not the most rigorous field. If doctors were trained like teachers, they'd insist that anyone with a problem with leeches didn't know what healing really is.

Here's some evidence: http://www.evidencebasedteaching.org.au/crash-course-evidence-based-teaching/6-misleading-myths-education/

Myth 1: Your Teaching Degree Helped You To Be A Better Teacher

The problem is that teaching degrees promote and peddle theory.

Myth 2: Children Learn Best When They Discover Things On Their Own

This myth is promoted in many teaching courses (see Myth 1), and it is reinforced by educational systems whose staff were indoctrinated many years ago. However, it is a myth because it based on a theory (i.e. someone’s idea about how learners learn) rather than on evidence.

Research shows that when teachers actively teach kids, they have over 3 times the effect on students’ results than they do when try to facilitate learning.

Myth 3: Children Learn More When They Have Control Over Their Learning

See Myth 1. Again.

Research shows that giving students control over or choice about what they learn has absolutely no impact on their subsequent results. Interestingly, giving students choices about trivial things (e.g. what colour pen to write in) does have small but positive effect on student outcomes.

Myth 4: Children Learn Better When You Cater To Their Learning Style

See Myth 1. Again.

The only thing more over-rated than Gardener is Myers Briggs.

Myth 5: Repeating Kids Helps But Accelerating Them Doesn’t

The complete opposite is true.

Myth 6: Special Diets Help Behaviour

At least where now into myths that parents believe, not teachers.

I'm not blaming teachers. Most of them know better. It's only the ones who don't who teach teachers, and the ones who aren't even good for that set education policy.