IQ is static because teachers literally can't teach anything. Their inability to raise IQ is because their teaching methods are awful, not because IQ is genetically determined. When students learn stuff, it's primarily because they manage to figure it out themselves.
Broadly, teaching methods are authoritarian and non-Popperian, among other critical flaws.
Concretely, math teachers don't know how to explain division and don't really even know how to teach counting. Lots of kids just figure out counting on their own. Like consider a group of 20 marbles. How do you count them? You need an organized method such as lining them up then counting along the line while keeping your place with your finger, or moving them into a second pile as you count them. Teachers routinely can't and don't even teach that much. You can read textbooks, curriculums, lessons, etc, and it's so bad in every field (not just math).
I already knew teachers sucked and stuff about IQ was wrong. Today I put those together. The failure of teachers to raise IQs is evidence that they are bad teachers. (It's not, as people normally claim, evidence that IQ is super hard to increase. Of course teachers who can't teach basic reading/writing/math also can't increase IQs with their teaching.)