I was one of those Catholic school kids who was left handed. The nuns set to trying to make me write with my right hand, which failed since I immediately went back to my left hand when they were out of sight. But I did learn skills that came in handy - being ambidextrous, for example. I also learned to write under my jacket so they couldn't see which hand I was using.
In my parochial elementary school, we were taught penmanship as a separate subject which you could fail. I was reminded of that quite often because not only was I left handed but my handwriting (perhaps as a result of having to switch hands) was illegible. In fact, in a desperate move to pass penmanship in fourth grade, I began to write so small that no one could read it. I recall teachers holding my marble composition book upside down and sideways and taking a magnifying glass to it prior to writing a big red F on top.
So that's the story of how I graduated from Catholic elementary school with handwriting that looked like hieroglyphics. Flunking penmanship did not hold me back in life as I feared. Of course now I can't write at all because my hands are paralyzed. It's a bit of a relief actually.
If you went to Catholic school, you probably learned to write with the method seen in the video below. Ahhh, memories.