School action varies hugely. If there are a multitude of kids on level 2 (does happen, not always the fault of the school) then 1 specific child won't be a priority. But yes in most average classrooms (where most of your children would be 3as, some lower some higher) she would stand out and should be recieving support.
There is no real formula like 2 years behind = action. You cannot generalise your experiences with your children's school across the whole of education. The statement process is more regulated but again is individual. A child could only be a little behind but have a statement for physical, social, emotional and so on.
It confuses me that so many people assume she is dyslexic. I have taught many children who are behind but few who are dyslexic (yes accepting the fact that some may simply have not be diagnosed yet). Dyslexia is a spectrum of specific difficulties with reading and writing, very different to just a general slower understanding.
OP: what the teacher say? I can;t imagine she said 'X is a level 2 for writing' and then just moved on? She probably didn't go into details about the support she gets in class because she might think parents would be bored or confused by all that - this doesn't mean she isn't gettting support in class.
If you aren't satisfied with what she said I would certainly go in. Simply say that you think more should be done and you're supporting the class teacher in that. Often the teacher is crying out for resources and the SENCO or Head won't give them the time of day.
Go see the SENCO but keep the teacher informed at all times so she doesn't think you're "telling" on her.