schooldigger.com ranks schools based on percentage of students passing the MSA. I believe they also look specifically at how the special ed kids are doing.
In my opinion, if a school does a bad job with its LD kids, they will sink in this rating. If they are educating their special ed kids well, (and their ESOL kids) or if they don't have a lot of them, they will do better.
Keep in mind also that schools are only rated based on how well subgroups are doing -- such as Special Ed or ESOL -- if they have a certain number of students in each group. I believe anything under 20 kids per group and it doesn't count. So a school MAY be high because they are doing a great job with their subgroups. Or they may be high because their subgroups tanked, but they only had 15 instead of 20 of them.
Here's the list of PG schools... ranked by # in the state of MD. (ignore the first three schools which are the three lowest performing schools in MCPS)
http://www.schooldigger.com/go/MD/schoolrank.aspx?sortexp=LEANAME&sortdir=a&year=2012&findletter=P
#19 in the state -- Tulip Grove (Bowie) -- up 51 ranks since last year
#50 in the state -- Capitol Heights (Capitol Heights) - up 302 ranks - TAG magnet school but open to neighborhood children
#51 Heather Hills - down 26 ranks from last year TAG magnet school but open to neighborhood children
#76 Robert Goddard French Immersion -- open by lottery - up 15 points from last year
#188 Glen Arden Woods -- TAH magnet school -- no longer open to neighborhood kids - all TAG school -- up 20 points