More from The Atlantic article:
"These findings are troubling, but not surprising, said Richard Weissbourd, the director of the Human Development and Psychology program at the Harvard Graduate School of Education. “To be attractive to parents,” private schools in particular, Weissbourd said, “need to be able to tout how many of their students went to selective colleges. So they’re incentivized to give better grades.”
The same concern about college admission drives parents of students in suburban schools to pressure principals and teachers, he said. “It becomes very high maintenance for schools to deal with aggressive parents. So that can also push grades up.”
Then the cycle repeats.
“This is one of those things that works like a contagion,” Weissbourd said. “If you’re an independent school or a suburban school and you’re giving Bs and the school in the next community is giving A-minuses, you start to feel like those kids are going to get a leg up. So you start giving out A-minuses.”