OMFG. Teach by all means. And get yourself into a private school.
I didn't do this. I didn't have a PGCE or whatever it's called now. So I did Supply. I blush to say this now, but I wanted to teach.
Unfortunately, that is not what Supply is about.
Supply is the regular teacher has had a breakdown/has been double booked with an exam/their car has broken down because on a teacher's salary they can't afford a decent car that doesn't break down/they just cannot f*ing face another day of this and called in sick.
You will, or won't get a phone call at 07:50 am. You'd better be up and dressed and ready to get in your car. Yes, obviously, you might not have work that day, but as Supply you're worth slightly less than s**t.
Wnen you get there - this happened to me - you could be in the car-park when the agency phones to say - "Oops, sorry, they cancelled." Your day is now F*ed and you aren't getting paid for it. Let's assume they didn't make that call and you're actually checked in to the school.
Great. First you have to find the classroom. "It's over there, turn left at the canteem, keep going past Gym and you'll find it" passes for a comprehensive induction. But now the lesson plan. It could be German, Science, RE., or, God forbid, your subject, the one you know a bit about. The record was a two-sentence lesson plan.
Two sentences. No context, no warnings, no direction. Forget all that crap. You aren't there to teach. You're there to fuflfill the quasi-legal requirement to cover that lesson and try to make sure nobody actually dies during it. Catch a kid with a knife in class, jabbing another pupil OMG SORRY, I meant learner? Good luck, because you won't get any backup. Matey will be back in your next cover as large as life, secure in the knowledge that nothing is going to happen to him.
It's brilliant when the kid who couldn't do anything one day can, thanks to you. There is no other feeling like it. You might, might, might, have actually changed somebody's life.
But the chances of doing that as Supply are vanishingly small. Private/public school kids can be an utterly entitled pain in the arse. But there is some expectation that you're supposed to be there as more than a child-minder.
Don't do Supply.