Students at all-girls St. Joseph's Academy in the St. Louis suburb of Frontenac, Mo., wanted to have McCaskill speak at their commencement this month, McCaskill spokeswoman Adrianne Marsh said Tuesday.
But the offer was rescinded last week. The president of St. Joseph's, Sister Michaela Zahner, said she reluctantly made the decision after receiving a call from the St. Louis Archdiocese.
McCaskill narrowly defeated Republican incumbent Sen. Jim Talent last November in a race in which embryonic stem cell research was a key issue. A McCaskill ad featuring actor Michael J. Fox — swaying noticeably from the effects of Parkinson's disease — drew nationwide attention.
Marsh said the senator, a Catholic, understands that her positions supporting abortion rights and stem cell research are different from those held by the church.
The senator was told by the school that the decision came from Archbishop Raymond Burke, Marsh said.
"I'm disappointed that the archbishop has made this decision," McCaskill said in a statement. "It does not diminish my respect and admiration for St. Joseph's Academy, their faculty, and students."
A spokeswoman for the archdiocese, Anne Steffens, said the decision was not made by the archbishop. But Zahner said an archdiocese policy forbidding a public forum for speakers who diverge from church teaching clearly reflects Burke's position.
While St. Joseph's is a private, rather than an archdiocesan school, it receives its right to be identified as a Catholic institution through the archdiocese, Zahner said, adding that rescinding the invitation "was a very hard decision."