The headmaster of a prestigious Westchester private school resigned last week just days after his successor at a renowned Chicago prep school announced his shock resignation — as a probe into their connection to a Jewish student’s suicide wraps up. Randall Dunn resigned from his $960,000 post as headmaster of posh Rye Country Day School, on Jan. 22, just eight days after his successor at the elite Latin School of Chicago, Thomas Hagerman, abruptly announced he was calling it quits. “It is highly unusual for heads of private schools to announce their resignation in January,” a source familiar with the...