Private schools are fund-raising pros. They keep detailed tabs on families and alumni so they know whom to ask for annual funds, auctions and capital campaigns.

But recently, one of the top Manhattan private schools, the Dalton School, might have been a little too open with the data it had about some graduates. The school said Thursday that it had given out to some alumni who had volunteered to raise money for Dalton information about several other alumni whose own children had applied to the school. The information included whether those children had been admitted, information that most parents prefer not to be shared, especially in cases where the answer is no.

“It’s horrible,” said one alumna who has been financially supportive of the school, and like nearly everyone interviewed about what happened, declined to be identified for fear of upsetting school leaders. “Why should anyone know how much I have given and whether my kid got in or didn’t get in or even applied?”

The information leak, which was reported in The New York Post on Thursday, apparently began with good intentions. In November, according to a letter Dalton wrote Thursday to members of its community, a committee of 12 alumni from one class met to make plans for a reunion and for raising money for a class gift to the school. The committee was then given a list of 11 of their classmates whose children had applied to the school, and their admissions history; three of those were applying for admission for the coming year. The letter did not say how many of the applicants had been admitted.