At A Level it is usual to have 2 teachers per subject.
At GCSE (apart from sciences) it isn’t usual or recommended, but is increasingly common. It all comes down to timetablimg and school finances.
Lots of students also experience teacher turnover, especially across a 3 year GCSE course. Some could have more than 5 teachers across their GCSE course in just 1 subject.
It is one of the areas where independent schools’ extra funding makes a difference as they have more flexibility for timetabling so you’d expect just 1 teacher per subject at GCSE. Schools doing dual award science might have 2 or 3 and those doing separate sciences would have specialists for each science.
There’s nothing you can really do about it. It’s a feature of funding squeezes. Teachers already teach their max periods and tight timetabling with no slack means the same teacher often cannot be scheduled for all lessons. It results in 2 week timetables and often 2 or 3 teachers, esp in subjects that have more periods such as Maths or English. Add in a couple of part time teachers or SLT who don’t teach many periods and it can be loads of teachers. Teachers will usually split the course according to how many periods they have and take different topics. It works well in some subjects but less so in those that require prior knowledge and more building blocks. There can be advantages if a child doesn’t like/get on with 1 teacher, but also mixed messages about technique etc.
Secondary isn’t like primary…it’s not a job share of 1 class and there probably won’t be much liaising between teachers - those teachers might share 4 or 5 classes or more with another teacher.
It’s a great pity, along with the squeezing out of some of the creative subjects that can’t muster large numbers at options time, and limited options to boost curriculum numbers in certain areas so large classes can be run at the cheaper stage ‘per head’ price, never mind whether those subjects are actually what the students want to do or will give them the best opportunities at the next stage.