An atheist group says a school board in South Carolina is to blame for a valedictorian's decision to violate the non-prayer policy at his graduation ceremony.

The Freedom From Religious Foundation claimed that the Pickens County School District had created an atmosphere where Christian proselytizing was acceptable, indirectly encouraging the 18-year-old student to lead the crowd in a recitation of the Lord's Prayer.

"The valedictorian who so insensitively inflicted Christian prayer on a captive audience at a secular graduation ceremony is a product of a school district which itself has set an unconstitutional example by hosting school board prayer," said Annie Laurie Gaylor, FFRF co-president.

The atheist group said it had sent numerous letters to the school district, warning that Christian prayers at its monthly meetings were unconstitutional. Earlier this year, the FFRF accused the school district of discriminatory hiring, improper promotion of Christianity by faculty members, and inappropriate religious posters.

Facing potential lawsuits, the school district had decided to no longer include prayer at graduation ceremonies. But Roy Costner IV on June 3 deviated from his previously-approved valedictorian speech to talk about his faith and deliver the Lord's prayer.

"God’s such a big, important part of our life with everything going on, our community really needed it," Costner told The Blaze. "Our community is really strongly opposed to the school district’s decision to remove prayer."

Watch his speech, uploaded to YouTube, below: