Drugs? Sex? Rock and roll? Whatever it was, it made Mama turn them in and somehow got a radical priest involved. What say you?
Paul Simon says he has no idea, although it was maybe sexual. Basically, they were just lyrics that worked. So your imagination can just run wild.
I always thought they got caught in a compromising situation, which would have been harder to accept back in the 70’s, both being guys…
The song doesn’t say they did anything down by the schoolyard, it says they will meet down at the schoolyard after whatever mama saw.
When I’m 90, I’ll still remember Paul Simon beating Connie Hawkins in a game of pick-up.
I’ve always thought it was a three-way involving Rosie, the Queen of Corona.
Whatever it was, it was against the law.
I thought they were gonna meet to smoke a J. He also smokes a J Late in The Evening. 
I always figured it had something to do with drugs, but admittedly never gave it a lot of thought.
This may be way off-base, but I also thought Rosie the Queen of Corona was Mama. Paul goes “on his way” to get away from her and her wrath. He’s not saying goodbye regretfully, but more in a “good riddance” sort of way, and “Queen of Corona” is a derisive title describing the bossy matriarchal type.
That sounds reasonable. But on the other hand, would it get them all on the cover of Newsweek???
Maybe in the '70’s not such a big deal these days. Maybe get them sent to a house of detention.
Too bad he didn’t capture it all on Kodachrome.
He loved him like a rock.
To cite this:
In a July 20, 1972 interview for Rolling Stone, Jon Landau asked: “What is it that the mama saw? The whole world wants to know.” Simon replied “I have no idea what it is… Something sexual is what I imagine, but when I say ‘something’, I never bothered to figure out what it was. Didn’t make any difference to me.”
from Wikipedia.
Paul will love this thread if he stumbles on it. Lyrics knowledge!!!
His real name is Julio, but everyone just called him Al.
[Grumpy Old Man] If Simon can’t be bothered, why should we even care? Stupid song. And he could never beat the Hawk in one on one. And, for that matter, what are the other 46 ways to leave your lover? [GOM]
I thought “Queen of Corona” was latino slang for holy virgin.
Just for the record, it’s “see you, me and Julio” whatever it is, it’s a three way.
Corona is a neighborhood in Queens. So whoever Rosie was, that’s where she lived. It’s a predominantly Hispanic area these days (and could also have been when Simon wrote this). Fits with the name Julio too.
Well, the Simon quote above takes the mystery out of it but this was my assumption. For the era, it just seemed to fit for something that would cause your mother to disown you, your father ready to discipline you and a radical social justice priest to advocate for your cause and get you onto Newsweek.