The teacher asked the class who believed in God. I am a Catholic Christian, so I raised my hand. Most of my other classmates did as well. She sort of had this smirk on her face when she asked everyone to pray to God for anything they wanted – so of course you could hear all of the children, including myself, praying. We prayed for mostly bikes, toys and other innocent things a five year old would pray for.

After we were done with our prayers, the teacher asked us all to open our eyes and see if all the things we prayed for God to give us were there. Of course there was nothing there, just us. So the teacher asked us to close our eyes again and pray to Fidel Castro for a piece of chocolate candy. We all closed our eyes and asked for the candy.

At that moment I could see from the corner of my eyes as my head was down, the teacher had a bag with her, and was dropping a piece of what looked like candy on each of our tables. When she was finished she asked us all to open our eyes and see if Fidel Castro was generous to give us the candy we had prayed for. Most of the students cheered in laughter and glee at how great Fidel Castro was.

first link on google -> https://news.unclesamsmisguidedchildren.com/communist-indoctrination-exchanging-a-piece-of-candy-for-truth/

I don't remember this being about Cuba and Castro specifically, but when I was a kid this story was taught somewhere like it was a big deal.