I always thought you had to have done a curriculum subject at degree level, but I'm noticing lots of people training with science-ish degrees, but not one of the 3 curriculum sciences, so they might have a degree in geology or forensic science, instead of chemistry, physics or biology.
They always seem to want to do chemistry as well, and I'm not convinced that over 50% of a geology or forensic science degree is chemistry?
The ones I've met all really struggled - as people they were brilliant and knew their main weakness was lack of subject knowledge, but the work they were having to put in to bridge that gap, on top of having to learn to teach was ridiculous. It almost sets them up to fail.