According to this NYTimes article, a secret 1993 agreement between the IRS and the Church of Scientology lets Scientologists deduct the cost of a religious education as a charitable gift. The secret ruling appeared to come to light when the Sklar’s, who are Jewish, attempted to take a deduction for the religious portion of their children’s education at a Hebrew school. The IRS wrote them back asking for receipts from the Church of Scientology! The Sklar’s provided receipts from the Hebrew school and the IRS denied the deduction. The Sklar’s are now suing on the basis that all religions, or none, should be offered the deduction.
The secret agreement seems to have been leaked but no one knows for sure since the both the IRS and the Scientologists are fighting the subpoena demanding its release.
The world is always more bizarre than I imagine.