When did the use of formal, seminary-type education begin and why? When did it become the norm for church leaders to get a formal Christian education and why did that process begin?

When I say formal education I'm not talking about the mentor/mentee style that Jesus did with his disciples.

I'm talking about the following scenario:


A person independently enrolls in a Bible School/Seminary/Divinity school
They get a degree
They apply for pastor jobs and get hired as a pastor somewhere


The reason I ask is because the aforementioned process isn't implied anywhere in scripture. The idea of it had to have come from somewhere and for some reason.



Similar to this question, but I'm not asking whether or not this practice is supported by Scripture—I'm asking when it started and why it started.
First let me correct the assumption that the model you describe is normal for Christian pastors. It is in fact only a minority that follow this. The vast majority of Christian churches, including Catholic, Anglican, Lutheran and Presbyterians follow an entirely different model. In this model they:


Discern whether or not the person has a calling to Christian leadership
Send them for education as necessary. This will virtually always include some formal education, but not necessarily.
Appoint them to a leadership position


Even among those churches where the model you describe is used, it is not exclusive. I have encountered Baptist, Mennonite and other churches where they will find a person who is gifted in a pastoral or leadership area and appoint them to that role. They may or may not then send them for other training (formal or informal) as part of their duties.

However to start answering your question, which is about when it became normal to give church leaders formal education, it has been normal for Church leaders to receive formal education for as long as there has been formal education. Early universities were started as clergy training institutions, and only later developed into general education institutions.