Any Math Geniuses Have a Baby about 8 years ago?

The girls take a standardized test cold (aka unprepared) every year to test their progress.  The purpose of the test is to see exactly where they stand in comparison to 1. all children their age in public and private 2. all children in private 3. all children in a classic education private school (like the one where they go). 

Like the teachers, I have never paid much attention to it. We are told about a week before the testing that they will be tested. A month or so later, we get the results.

Obviously, I make sure the scores are above a certain range.

Because Sarah is only in second grade, she is only compared to private schools, and in order to be compared to all schools, we are supposed to add 2 to 3 points to the ranking. Ranking is based off a percentage--for example better than 56% is a 5.  Her first scores were good. I thought they might be higher but it was her first test like this. (Honestly, she talked for days about how a computer was going to grade her paper and she had to fill in circles completely 'for the computer grader'). 

And then I got to math.

She scored better than 99% of all private school peers putting her in a 9 ranking.  I always knew Sarah was good at math but better than 99% of her peers?! I am good at math but not that good. That score was Einstein good. I thought it might be a common thing for that group and not something to get too excited about.

Sarah looked at her scores and asked why  she didn't have the third set of numbers like her sister. I explained they did not have public school comparison and to get that number you need to add 2-3 or 20-30% to percentage.

"But you can't add more 1 to 99%. You can't go higher than 100%."

It was then and there that I realized two things. One: The test was right and two: some nurse switched babies on me in the hospital.