Does teacher training improve schools?

What follows is a comment posted on the website of a national newspaper.

I went to a grammar school in Birmingham in the 1960s. None of my teachers went to teachers training college. They either came from University with a first class degree in the subject they taught or they were ex officers from the armed forces who knew how to instill good discipline and command respect. The school had an outstanding record for the numbers of its students achieving university places. By not going to TTC, they were not indoctrinated with the usual left wing liberal claptrap that seems to be the case nowadays. And yes, we did have corporal punishment but it was used only as a last resort. That ultimate sanction prevented the more unruly boys from stepping too far over the line of bad behaviour.

For many decades now, British schools have had little choice when recruiting teachers.  So far as I am aware, they have been required by law to recruit only teachers who have acquired certain documented qualifications, and yet this policy has not prevented us from having many failing schools over the years.

Suppose you are the chair of governors at a failing school.  You want to dismiss those staff members who are letting the side down, but you know that you will then have to recruit people to replace them, and your choice will be limited.  What if the replacement teachers also let the side down?

Maybe now is the time to consider the likelihood that legal restraints on teacher recruitment do more harm than good.  Regardless of whether or not it is true that trainee teachers are indoctrinated with the usual left wing liberal claptrap as is implied above, it is nevertheless true that legal restraints have not delivered world class schools.