If you teach secondary, you need to therefore be an "expert" in one field at least. So you need to study it to degree level. Then you can do a PGCE in that subject, in secondary level. You can also do a Junior school PGCE. If you want to teach Primary you still have to to 4 years study. It is a BEd (Batchelor of education) which you do as a degree. ie- it is still a degree, but the whole thing is geared towards teaching primary level. Whereas the secondary PGCE is a very quick course on education, classroom management techniques and teaching practice. The assumption is that you already have the "knowledge" to teach the subject, the PGCE just knocks you into shape so you can cope in a classroom. At least, mine did! It was never about "how to teach maths", it was about how to teach.