Actual teaching is a fantastic job. I now teach in a fairly small independent school, and I think my job is probably quite close to what people imagine. I do spend a lot of time preparing good lessons, but that's because I know that the kids will then be engaged and make good progress. I spend a huge amount of time marking, but I know the kids will read the comments, and respect my input. And the lessons themselves are usually quite good fun. Sometimes we go off on a bit of tangent, and we have a bit of a laugh, but we can back on track quickly, and every hour feels genuinely productive.
This is miles away from my last job in a (well respected, over subscribed) comprehensive. Controlling crowds of rude, aggressive kids whilst feeling desperately guilty for the quiet ones who did want to learn but never got the chance. Feeling sick going to bed, because I knew I'd have to do it all again tomorrow. Actually hoping I might crash my car on the way to work so I wouldn't have to deal with year 11 period 1. "Free" periods taken up with cover for colleagues who hadn't been able to face coming in.
It's not really the kids that are the problem. 30-32 (or even 34) is completely normalised as an acceptable class size, but it's too big. 24 is a completely different thing. There are physically not enough hours in the day to do a good job of full time teaching timetable. Teachers are running on caffeine and adrenaline, they spend all their time logging behavioural incidents, and then marking books for constant "work scrutiny", so they have no time to prepare good lessons. Unsurprisingly this means that they're always on the back foot, behaviour gets worse, and the teacher has no head space, or patience, or energy to deal with it.
OFSTED has such lofty expectations of schools, which are so far removed from the reality of the conditions in which teachers are working. Good lessons and good classroom management should always come first, and it should be understood that at some points most teachers will have to let everything else slide just to focus of those two key things.
(sorry for that rant- I think I'm still processing the trauma of just 3 years in what really was not a particularly challenging school!)