Exactly , the top 10 maps you see on your profile count !
http://et.trackbase.net/index.php?mo...fo&idx=1035081
School is in top 3 of your maps played which means its an important one. dont know you ppm avg there but it must be something around 18.50 ppm , you have 13.3h time played there sp 13,3x60 =798 / 30 = 26.6 so basicly you played it 27 times ( 30 mins for each times which isnt 100 % sure , sometimes map can be ended earlier so 27 is the minium of times you played that map )
But many factors are behind like your own Rating is highter (23) than that kontraks guy (16) avg ppm etc etc
On that map from now on you need minimum 18.50-19 ppm to get + according to ppm avg if it stays around 8-9.
Its not new , and its working like that on SL too , your TOP maps are important .
If you get 16 ppm on school , you can get -0.20 for example , since its an important map