Saint John was an ordinary man, the son of a fisherman, with a limited education.
I agree and like the post, but make the following observations.
I don’t know about the “limited education” part.
St. John was the youngest of the Apostles. And one of the only 2 Apostle who did not run away from our Lord when the Pharisees came to apprehend him. In fact, by his own admission, he was permitted to enter the chamber of the inquisition which was held against our Lord:
John 18:15New American Bible (Revised Edition) (NABRE)
15 Simon Peter and another disciple[a] followed Jesus. Now the other disciple was known to the high priest, and he entered the courtyard of the High Priest with Jesus.
Since, St. John, was a son of a fisherman, yet well known by the High Priest, that leads me to believe that he was moonlighting, so to speak, and studying in the Temple. Perhaps under the tutelage of the High Priest.
Another detail, which is overlooked, but St. John was not accosted for his relationship to Christ as some tried to embroil St. Peter.
John 18:16….The other disciple, who was known to the high priest, came back, spoke to the servant girl on duty there and brought Peter in. 17 “You aren’t one of this man’s disciples too, are you?” she asked Peter.
Everyone in the court seemed to know that St. John was a disciple of Christ. I don’t know if I’m reading into it, but they sound hostile towards St. Peter but they weren’t hostile towards St. John, proof is that they let him in the door. But, perhaps, because of his young age, he was not considered a threat.