I’ve never heard thhat, but on another thread there was a variation where somebody said that someone else told HIM that “the first time you go to a Catholic Church you get three prayers answered; this only happens the FIRST time”.
All I can say is, mommy, ALL our prayers are HEARD by God, no matter whether it’s our First Communion or not. And all our prayers are ANSWERED by God–even if it’s not the answer we want to hear. But to say that any prayer is “granted” by God smacks of superstition. I’ll be charitable and think that the priest himself thinks of “grant” as the same as “answers”, and that it was just a less than optimal word choice for what the priest actually believes. . .
But please don’t think that God “owes” us a First Communion freebie.