During much of history, few people were taught to read and write. Priests had to be able to read the Bible as well as other documents in the course of their duty. Those that were lucky enough to have a calling to service with the church were taught these skills. Because of the church's need for literacy, they were often centers of learning. They taught religious lessons to the faithful in their community. Children being raised in the faith were given religious instruction.
Over time, governments learned that educating their people made for better societies. The church had long learned that lesson, but had few enough priests to spread the knowledge. Rather than teaching many people to read and write, they simply preserved knowledge for future generations. Churches today have mostly restricted their teaching to religious lessons. There are some churches that have their own private schools. These schools combine government mandated academic learning with religious training.