Percentiles can be a bit misleading. If half the class of 31 got 100% then the 16th kid who got 99% would be at about the 50th percentile. The difference in the scores suggests there was something like that going on. When they somehow? Forced the results into a normal distribution some kids went down. They may have added an age rather than grade rating - eg 100% at 7.8 beats 100% at 7.9 etc.

Ok I cross posted. Disregard the second part of the post.

Last edited by puffin; 12/03/14 09:18 PM.