Teaching school used to be a mostly volunteer job taken on by parents in the community. They knew their kids and the other kids their kids played with in their neighborhood. Wives whose husbands provided for the family left them able to teach. And sometimes men who made a lot or were retired or could ask for time off from work to teach because everyone knew it was important. Often the men taught math and science because the wives couldn't. When teaching became a profession and worse one that required credentials before you could set foot in a classroom it became a problem that has put us where we are today.