Will Shortz always ends the Sunday Puzzle portion of NPR with the next Puzzle - folks send in answers and a winner is picked to do a puzzle on the radio the following week.
I am not a puzzle guy, but listen. This time he referenced an old poetry book from over 100 years ago that apparently had a section on Poetry Puzzles. One of them did not come with a published answer, so he offered it as the puzzle this week.
It is kind of like the Riddle of the Sphinx:
What do you think?
…
At Choate Rosemary Hall
Where I had quite a ball
Now I pitch probiotic stew.
A Clownfish
Teachers?
Oooooo!
What no “Oooooo” for my answer? 
The largest, most dominant male Clown Fish changes sex when the dominant female dies, so they are literally both male and female. There are mainly males (boys) in the school with one dominant female. Maybe it isn’t what was intended, but it fits.
Jamie Lee Curtis
Perfect answer.
Sorry - a late “Oooooo!” 
I actually thought of that, too - not specifically clownfish but gender-switching species. But the riddle is from a poetry book from I think the late 1800’s. I really would be surprised if they were looking to that type of biological answer.
Very open to being wrong, just articulating my thinking.
That’s the first thing I thought of myself, but then thought that I’ve never seen clownfish school, and after Googling, it appears they don’t. But I’m sure all this is way too technical for a simple riddle.
I’m a little young to know the state of biology awareness in the late 1800’s (couldn’t they just Google it?).
Sometimes riddles have more than one answer… What’s black and white and red/read all over… a newspaper/a zebra with diaper rash.
For the original riddle… a teacher/a Clown Fish/a Hermaphrodite at Eton.
They don’t school like we normally think of with fish swimming together to make them look bigger, but they do have a “colony” which is a social group of the same fish. They live in an area among the anemones nearby. I very well could be wrong, but I think any colony of fish is still considered a school. I’m very open to having my ignorance fought. I’m not really a fish guy… just a diver who picked up on what he heard.
A ruler could be a man or a woman…
Could it be an author, assigned in schools, who happens to be a woman that wrote under a man’s name? You know, like George Eliot? Or a woman who had a last name like “Mann”, or a man who – well, okay, “Woman” isn’t a terribly likely last name, but something like “Lewis Carroll” is getting there; “James Shirley”, f’rinstance?
A ruler.
This. The clown fish is a great answer, but they wouldn’t have used it that long ago. A pun, like ruler, is more in that period’s style.
The fact that “ruler” has two meanings makes me think it’s more likely the answer. That seems to be the source of humor in many of these riddles.
Plus, I’m actually starting to think I may have heard this joke before. I know I’ve heard a joke that involves schools and the double meaning of “rulers.”
Nice. We’ll have to hear what Shortz says next weekend, but ruler sounds like a great fit.
I don’t think he knows the answer. It is a riddle published in a newspaper in 1803* without an answer given, and collected in a book. He’s looking if anyone can give a convincing answer.
It’s described as a rebus. Today this means a picture puzzle, but at the time it appears to have meant the type of acrostic puzzle where each line gives a clue to one letter in the word.
*It’s actually older than that.
That’s correct - he stated there was no published answer, so he would allow any answers he thought qualified. I assume ruler would be one he would allow.
Hey, perhaps he’ll allow clownfish!