All children do not necessarily make progress in a standard, linear fashion, for a range of reasons. My DD for example was behind in Year 2 in most areas apart from reading. Later an ed psych diagnosed dyslexia (though she does not have all the typical traits one might associate with dyslexia). She is also lucky enough to be very bright, and now she is secondary age comes top or near the top in exams in most subjects in a selective private school....
And that sounds like I am showing off about her a I don't mean to! (I am massively proud of her yes, but because she is lovely, not because she is fortunate enough to be good at academics).
But I would urge you not to panic. I was beyond stressed out when my daughter was little, and bought all these work books and things and would spend hours doing them at home - it made no difference to her learning in retrospect, but actually damaged my relationship with her at the time I feel! She certainly remembers them with horror. Luckily we got over it and are very close now.... And in terms of learning, after a few years, things just came together for her! Well more than came together - she is now absolutely thriving....
OP, there is loads of time for your daughter to catch up, if she is indeed behind due to poor teaching, as you feel. Learn from my mistakes, and please don't stress out over it, as that stress can easily communicate to her as well. If you start her on a good state primary next year she will catch up I have no doubt - and if there IS a specific learning need such as dyslexia holding her back (and I am in no way suggesting this is the case - it's one of 100s of possibilities) the teachers there should be in a strong position to identify and support.
Good luck. And don't blame yourself. If she has been happy enough in the school for the first two years, emotionally well adjusted etc, I would say that is the most pressing matter at this stage.