FFRF made a Pennsylvania public school discontinue graduation practice inside a church.
Columbia High School last year required its students to receive their graduation caps and gowns and ceremony information within a church.
School districts that have used churches for school functions have had the practice struck down by courts.
"A school's use of a church for school functions is problematic because it sends a message of approval of the church to impressionable students," FFRF Legal Fellow Madeline Ziegler wrote in a letter last July to Carol Powell, then-superintendent of the Columbia Borough School District.
On receiving no reply, Ziegler followed up with two more letters in November and last month. Finally, FFRF got a response a few weeks ago from Acting Superintendent Ken Klawitter, who took over in December. Klawitter told the organization that he first became aware of the issue through its February letter and acted swiftly.
"I immediately directed the high school principal to cease the practice," he wrote. "In the future, caps and gowns, as well as important graduation information, will be distributed in a secular setting."