There are theories of learning, epistemologies of disciplines, management techniques and and something like 2000 pedagogy and content standards that have to be mastered at the elementary school level.
In the undergraduate Education programs at St. Michael's College where stduents can ultimately obtain a license to teach the role of theory and practice and the interplay between them are taken very seriously. From the very first Education course, students get to experience what it is like in a public school classroom. They get opportunities over and over again to experience what it is like to work with young children based on a solid grounding in theory in their coursework.
Over the years I have experienced all kinds of variations to this theme both directly and through the stories and experiences of colleagues. I once had a prospective student ask me which 3 credit course she needed to take to become an elementary school teacher. I've had students ask me if they can do their Education courses as independent studies and other students who said they didn't have time to fit in the field placement attached to a a course. I remember a story from an old friend from graduate school I met recently who was teaching in a small college in the Mid-west who said she had a student who was so poor in her student teaching experience that she was going to fail her until her program director discovered that she was a member of a family with which the director had a lifetime of close ties. The student teacher was just unable to put theory into practice, she said.
This last example is what I mean by "Mind the gap", a famous sign on every underground station in London. There is, of course a gap between theory and practice; just like between the train and the platform, that the student must negotiate with the help of her/his supervisor. I remember another student I was supervising in Illinois many years ago who, in the middle of reading a sotry to a class of first grade students, put the book down, burst into tears and said "I just can;t do this". She was a straight A student in her coursework but just could not negotiate the gap.
So when I'm working with anyone who wants to become a teacher I'm always aware of the gap that exists between theory and practice but also very aware that you can't have one without the other.