well, we do KNOW this about Obama's grades at Harvard Law School....
At Harvard Law School, Obama graduated Magna Cum Laude, which, according to the Havard Law School website, is awarded to the top 10% of Harvard Law School students.
Also at Harvard Law School, Obama was accepted as one of 85-90 Editors of the Harvard Law Review, out of an estimated 1,000 students from the 2L and 3L classes that might have sought this honor. Obama was also elected President of the Law Review, which according to a Harvard Law spokesperson is not based at all on academics, but on other measures as would occure in any club.