Alright, specifics:
The "shitty SLT" mentioned here (many I met have been lovely) comes down to lack of management training. Often, people who know how to get results or with the right level of time/ confidence are chosen for the job rather than those who are suited for management. They go into SLT without any management training. The same goes for anyone who is head of/ deputy head of department. So you can end up with a whole bunch of people good at talking the talk and fudging results, but with zero skills to actually lead a team.
Targets for students are so out of touch with reality that you will be put under huge pressure to get results. My school, like many, has yet to acknowledge that performance related pay is gone; we still have targets for results to meet on an individual basis in order to get pay progression. So if you get many bottom sets with lots of students not turning up to school on a regular basis and others not caring, you will be denied a move up the ladder, putting you under huge pressure to achieve and prove everything you did to try and prevent that.
Workling hours are looooong. I have people still emailing me at 10.30pm - sometimes colleagues, sometimes parents. Sometimes it can wait, but often a solution is required before teaching begins again the next day - often because of an issue with a pupil, which has to be addressed, or because everything is done evry much last-minute in many schools, even if you yourself are organised. So if you don't want to get into work the next day and have to deal with 15 emails while also trying to set up your teaching day, you respond and work late at night.
We get into work at 7.30, partly because many schools only have 2 working copiers for the whole school and everyone needs one, partly because meetings start at 8.15am, up to 3x a week, and you need some time to set up. You teach until 3.15, then have duty, then after-school clubs or intervention or meetings so you don't actually finish contact time until 4.30. Then you make phone calls, tidy up, plan some stuff and whoosh it's 5.30 and you have to pick up your own kids. Then you sort them, after that you work - often marking is involved, too. You also have parents evenings and open evenings up to 12x a year at secondary level, and some twilight sessions run until 6pm, pushing everything else back.
Behaviour is worse than I've ever known it. A mixture of unsupportive, overly stressed and overworked parents not dealing with behaviour at home, management who have bought into the whole "building relationships" trope (which pushes all work and responsibility for behaviour onto you while giving you none of the support) and pupils who don't sleep, are addicted to tiktok and know they can get away with murder. You will have child criminals sitting in your classroom and children with anger issues so severe that they are a danger to themselves and others.
You will have zero time for yourself in school. PPA is given at the minimum schools can get away with, because there is no money to employ enough staff or to employ cover teachers. You will miss breaks to duty. You will have meetings in your PPA time. Lunches are often so short now that you don't have time to sit down and eat. You will not be able to go to the loo when you need to.
And there is no flexibility for you. I have had my heating break down this weekend. Do you know when I can get it fixed? Next weekend, thanks to a very generous engineer, who is prepared to work weekends. Not many are. That's because by the time I'm home he also has to look after his kids. So now I have a week without heating in the first big cold snap of the winter. I have had this happen with all sorts of things that I needed tradesmen for. Long waits if I was lucky, paying dodgy firms that subcontract on a 24/7 basis over the odds if I wasn't, because in many schools taking time off for such things as trying to have hot water at home is really frowned upon.
These are just some of the stressors. There are more.