I'm going to "shoot from the hip," here.
Of course the school should tell you your child's nc level. Of course you should be suspicious if they don't. I find it patronising and condescending for a school to take the attitude that parents couldn't possibly understand levels. More likely the school is afraid of being challenged.
I remember my first dd starting school and wondering what on earth was going on. There was no meaningful feedback, just platitudes and vague positive comments. I felt like I stepped through the looking glass. Then at the end of yr2, we were given a report with these strange numbers. Neither dh nor I had a clue. Another parent with two dc at the school had to explain.
Now, I know that at least where we live, these levels do matter. The levels they leave yr2 with form the basis of their yr6 projected levels. At our school, dd1 got ahead of her projected trajectory and spent a very dull yr4. Of course a school or teacher would say that the projections are just a guide, but in my experience, at our particular school, the subsequent teachers follow them closely. They will let a kid lean back and cruise if they are easily hitting levels, they will get really serious and focus in if a child is falling behind projections. I am told, in our LEA, the levels they leave yr6 with will form the basis of their initial streaming when they get to the local compressive.
I am sure things vary around the country, but from my vantage point, I can see why parents get a little uptight, even in infants. Kids seemed to be channelled quite early, and any caring parent would want their child to have the best chance possible.