Incredible story in this week's Pahad David - p. 2 that I will translate (Updated: I mistranslated גימנסיה so all references to "gym" were changed to "high school"):
This story was publicized in the new volume of the book "Veha'arev Na", and it deals with a Jewish boy from Baltimore who was very far from Judaism, and wanted to be accepted to learn a profession in a certain high school. Standing at the head of the high school was a priest, and when the boy approached him, the priest asked him if he was Jewish. The boy thought to himself, "What should I answer him? If I tell him the truth, maybe he won't accept me because I'm Jewish, and if I lie and say I'm not Jewish, maybe the truth will come out." In the end, he decided to say the truth.
When the priest heard that he was dealing with a Jewish boy, he asked him, "Do you recognize the letters of the Hebrew alphabet - the Alef Bet?" The boy answered, "No, I have no clue about them." The priest told him that he was accepted to the high school but on one condition: "that every afternoon, after you finish your lessons, you come to my office, and I will teach you the Alef Bet!" The boy, who really wanted to be accepted to the high school, had no choice but to agree to the strange request.
At the end of the first year, the boy finished learning with the priest all the letters of the Alef Bet. Then, the priest called him and informed him, "If you want to continue to learn in the high school next year, you will need to come to me and have a private lesson in Humash." The boy had no choice and again agreed to the strange request. At the end of the year, after the boy learned all of the 5 books of the Torah, the priest called him and told him that he could remain in the high school only if he comes next year to a private lesson - this time in Mishnayot. The boy again agreed to the request and throughout the year, the priest and the boy dealt with learning Mishnayot.
For the fourth year, the priest called the boy and told him, "If you want to continue your studies with us, you will now need to learn Gemara, but not here - in Yeshivas Ner Yisrael of Baltimore - which was not far from the high school. Rav Ruderman is the Rosh Yeshiva. He will teach you Gemara. After you learn Gemara there for a number of months, you can then return and learn in our high school." Leaving him no option, the boy again agreed, and approached Yeshivas Ner Yisrael to Hagaon Rav Yaakov Yitzchak Ruderman ZT"L to learn Gemara.
The boy entered the Yeshiva and looked for Rav Ruderman. When he found him, the rav asked him what he wanted. He answered, "I came to learn Gemara." The rav was very amazed since the boy didn't even look like he was Jewish. "Are you Jewish?" he asked. The boy answered positively. The rav told him that he cannot now teach him Gemara - "You first need to learn Alef Bet and reading." "I already know them - also, I already learned Humash and Mishnayot," the boy said. The rav tested him and he was proven correct. "Where did you learn Torah? Who sent you here?" wondered the rav. "The priest at the high school," answered the boy.
Rav Ruderman accepted him to the yeshiva, and already after a few weeks, the boy started changing his ways. The light of Torah had influenced him and brought him toward good. He got better and better until he became a true Ben Torah. After a half a year of tiring learning in the holy Yeshiva, he was tested on a complete Mesechet, and after he passed with flying colors, he received a certificate saying that he succeeded in the test on a complete Mesechet. He ran to show the priest.
The boy thanked him since it was in his merit that he returned to the source and grew in the yeshiva. "But I want to know one thing: why did you do this for me?"
The priest broke out crying and after he calmed down, he told the boy a story:
"Many years ago, I received a sabbatical from work and I didn't know how to spend the year. I heard about a group of priests who were traveling to the Land of Israel for a week and decided to join them.
"On Friday night, I got to the Kotel and when I heard Friday night prayers, I very much enjoyed them. I waited there until the end of prayers.
"At the end of the prayer, a Jew approached me and asked me if I have a place to eat on Shabbat. I replied negatively, so that Tzaddik gathered me into his home. After the meal, he asked if I would accompany him to an exciting Mussar talk by Rav Noach Weinberg and I happily agreed. I was very impressed by the talk. I decided that there is something for me to do on my sabbatical year - to remain in Yeshivat Aish Hatorah, headed by Rav Weinberg. I informed my peers that they should go on their way and that I would be remaining a bit longer in the Land of Israel.
"During the year, I had the chance to learn Alef Bet, the 5 books of the Torah, and Mishnayot. At the end of the year, I approached the rav that taught me and told him that my sabbatical is over and that I must return to my job. The rav tried to convince me to stay, saying, 'After you learned so much, it would be a shame for it all to go to waste,' but his persuasion did not help. He requested that we approach Rav Weinberg in order to hear his advice. Rav Weinberg also said that I should stay, and it would be a shame that I should leave after I was doing so well during the year.
"Finally, I decided to confess. 'I am going to tell the Rosh Yeshiva the truth. I am a Goy and serve as a priest, and I now need to return to my work.'
"Shaken, Rav Weinberg heard this and responded sharply, 'I do not forgive you for the entire year that you wasted for us! We invested so much in you for nothing!'
"I was stunned and started crying like a baby. I asked that he forgive me, but he resolutely said, 'There is no forgiveness for you, not in this world or the next world!' Eventually, he said, 'Maybe, you can get atonement if a Jew will by chance come to you and you will transmit to him everything you learned in the Yeshiva. Only then would it be retroactively clarified that your learning here wasn't totally for naught...'
"And now," concluded the priest his awesome story, "after years that I waited that a Jew should fall to my hands whom I will be able to teach, you came here. And in order to fulfill my promise, I tried my utmost to transmit to you everything that I learned in Yeshiva..."