The Dubliners did a version of the original as "The Kerry Recruit", where Mrs. McGrath's boy loses his leg, on an early album with Bobby Casey in place of Luke Kelly at that time. However, the one you want is the parody with Ciaran Bourke doing the singing (but not changing the name of Mrs. McGrath).
(Spoken introduction by Ronnie Drew)
Ciaran is the only member of the group whose father spent money to give him a university education. And would you believe that this is the result of it?
"O Mrs. McGrath," Dr. Tierney did brag,
"Send your son up to college where he can study ag.
He'll get a Volkswagen car and a tenner a week flat.
Mrs. McGrath, wouldn't you like that?"
Wid yer too ry aa, fol the diddle da
Too ry oo ry oo ry aa
Now Mrs. McGrath came from County Clare,
And for 47 or more years she'd lived there.
She was a milkin' cows and a feedin' pigs
To keep ould Ciaran in his Dublin digs.
But then one day, what a terrible shame,
As she swept out the kitchen now a letter came.
It bore bad news which was not expected.
Ciaran had failed four times and was now rejected.
(Spoken by Ciaran)
So Ciaran then wrote back to Daddy, and he said, "Dear Daddy . . .
It wasn't the work and it wasn't the strain,
And it wasn't on your own darling son that lay the blame.
But when I came up from Clare I was an innocent lad,
But the fellers in the digs they drove me to the bad.
O, I tried to stay in and work at night.
Sure, the fellers in the digs took me out in the spite.
And when you sent me my fees, now what do you think?
Sure, I spent all the money on the women and the drink.
Now the moral of the story is plain and clear -
Stay away from the women and keep off the beer.
And if you've got a son on the farm,
Keep the young pup there where he'll be out of harm.
HTML line breaks added. --JoeClone, 28-Jan-02.