WASHINGTON—According to a survey released Friday by the Pew Research Center, at least a majority of American children are deeply enmeshed with a public-school teacher having sex with them. "We've seen a marked decline in the quality of education for these kids," said Pew spokeswoman Wendy Teter, noting that many of the students in the survey were too ashamed to tell their teachers what was happening to them. "It's as if they don't even know their teachers—they're just there with them." Studies have shown that the number of children being taught by public-school teachers to find out what's going on and then to take turns having sex with them has dropped by more than half.