Here in the UK, people have employment rights, including the right not to be dismissed without process. That involves warning the employee twice verbally, putting in place measures to help them improve their performance, and then a final written warning. Teachers here are unionised; they can take their employer to an employment tribunal, which is a kind of court, for the offence of Unfair Dismissal. It takes time and money to fire someone for underperformance.

Consequently recruitment is done rather carefully - more carefully than in many software companies, judging by the calibre of some of the colleagues I've worked with.

FTR I used to be a school governor in a state-run primary school.