It is enjoyable, the teaching, yes, although don't make the mistake of thinking that everyone in an A-level classroom has chosen to be there, these days. There are very few alternatives for most 16 year olds.
Ithink the main issues for someone in your DH's position are a) the massive pay cut; b) teaching is very old-fashioned in many ways, with a lot of hierarchy - it can be painful to start over at the bottom; c) a lot of the job doesn't involve teaching at all. It's also pretty stressful especially when you're a beginner, because so many things are out of your control.
You need a good level of physical and mental health, patience and tolerance for bureaucracy much more than a knowledge of Economics. I know my subject well and work on improving my knowledge and skills, but I barely ever get observed by anyone with Economics knowledge. I could be talking utter bollocks for all they know.
So you also need to be someone not reliant on positive feedback from others, as you won't get much.
Teaching is a vocation, though. A few days in a classroom and it'll grab DH. Or not.