And how did he manage to become a 'qualified' primary school teacher in the first place? Qualified to do what, one wonders.
However, during my years as a school governor (1980s), when I was involved in teacher interviews for the school, I was horrified to find that most (yes, most) applicants, usually above a certain age, did not even have a basic maths O level pass to their name and yet were considered 'qualified' to teach maths to primary school kids. I did not feel confident of their grasp of mathematical concepts.
Swings and roundabouts.