From Reliable Source:

B Stung in ‘71, and It Still Smarts
The Education of a Senator, Day Two: Yesterday we told you about Chuck Schumer’s early years on the “It’s Academic” team in high school. Now we’ve learned that the brainy New Yorker (high school valedictorian, 1600 SAT score) is still steamed about the grade he got on his college thesis.
Schumer was a senior at Harvard in 1971 when he wrote the paper about building a more effective Congress — and furious when he received a B. His instructor? Conservative commentator Bill Bennett, a Harvard law student who was teaching the undergraduate social studies course. “He went nuts,” said Bennett, who was unmoved when Schumer lobbied for a higher grade.
Bennett said the senator still reminds him of the beef every time they meet. “He says, ‘I don’t know if you remember this . . .’ and I say, ‘Stop with the grade-grubbing.’ “
We wanted to hear why Schumer thought he deserved an A, but he didn’t get back to us yesterday. Bennett has finally relented — a little: “At this point, I’d be happy to review the paper.”