It was, in the vernacular of corporate America, a win-win: a bond that paid for preschool for underprivileged children in Utah while also making money for investors.

Goldman Sachs announced last month that its investment in a Utah preschool program had helped 109 “at-risk” kindergartners avoid special education. The investment also resulted in a $260,000 payout for the Wall Street firm, the first of many payments that is expected from the investment.

Gov. Gary R. Herbert of Utah hailed the program as a model for a new way of financing public projects. Such so-called social impact bonds are a new kind of public-private partnership, promising financing from Wall Street and imposing a goal on local governments.

Yet since the Utah results were disclosed, questions have emerged about whether the program achieved the success that was claimed. Nine early-education experts who reviewed the program for The New York Times quickly identified a number of irregularities in how the program’s success was measured, which seem to have led Goldman and the state to significantly overstate the effect that the investment had achieved in helping young children avoid special education.