I think it would be funny, but they certainly wouldn’t publish it, of a student who wrote that when he entered school he was an atheist, but *despite* their efforts to reinforce his atheism, he became a Christian.
Perhaps go on a while about how he discovered atheists were weak and unhappy people, determined to inflict atheism on others precisely because they were wracked with doubts about their atheist beliefs. How they felt isolated and alone, leading useless and empty lives, and destined for nothingness.
Maybe conclude by saying how much his teachers must be disappointed in him. That instead of pursuing a meaningless existence, he now has the solace and succor of faith, and feels the warmth of love and purpose in his life.
Such a letter would bug the heck out of them.
C.S.Lewis writes a story like that in his memoirs of his time at Oxford in the 1920s.