@AbsolutelyEmma I would see if you can read the school assessment policy. Some schools have parents’ evenings to explain it.
As a governor, I was always looking at assessment data. Not individual dc, but overall data for each class. First of all, our teachers assessed around 3 times a term. It was agonized over! Also work was sampled by other teachers to ensure accuracy. The assessment was based on what dc had been taught. Not what they hadn’t been taught.
In KS2, DC were set work based on their understanding of the topic. The dc who were working towards did revision of basics needed before a new topic. So tables, measuring, multiplication etc. Then they would be taught the topic and appropriate work set. That way the teacher can see who can do what anD accelerate dc where needed. Therefore of course you get exceeding, meeting and working towards. However not all classes will be the same. Very few could be exceeding. These dc should be getting extension topics. Others will improve with revision and practice. Some will remain as working towards.
The teachers are expected to keep the dc making progress but they have different starting points . With borderline dc this can be a bit yoyo as you are discovering. Neither do teachers always agree on progress made!
I would expect dc to be assessed more regularly than once a term. Thats actually too infrequently to put in intervention. So definitely ask about that. Can the teacher say what dc needs to do to get expected? You could then practice or guide dc at home. The teacher might have low expectations, which would be a worry.
Its fairly unusual for a teacher to not get salary progression due to this and it would depend if it was a target for their performance management. It would not be the only measure of their performance. Heads evaluate performance and make salary recommendations to the governors pay committee.