I am by no means a testing expert, but there is a certain amount of validity in what they are saying. Some kids are very early readers or know their numbers and basic math facts at an early age. Other kids will acquire these skills later, but catch up very quickly. The early readers and counters (for lack of a better term) will score disproportionately high when they are tested at an early age.
You also have to allow for the fact that many young kids may not be the most cooperative test-takers, even though they have the ability to obtain high scores. This also boosts the scores of those young kids who are both able and good test-takers.
This does NOT mean, however, that high scores at an early age will necessarily go down. In fact, they may be even higher in a few years time.
Back to your current issue, the fact that the school does not like to test until 2nd grade seems to me a poor reason not to address your child's needs now. If your DD needs some sort of accomodations now, these need to be addressed.
