A very long time ago (1960's or 70's, story may have been much older) I read a short story about a lazy boy who invents a robot so it can do all his work for him, the tagline in the story is "laziness is the mother of invention" thanks.
If you are misremembering stupidity as laziness you might be thinking of "Eurema's Dam", a 1972 short story by R. A. Lafferty which shared the Hugo award for best short story of that year. It was first published in New Dimensions II, an original-stories anthology edited by Robert Silverberg which you can borrow from the Internet Archive, or you can listen to a Mindwebs reading.
Albert is a boy who invents robots to do all the things he is too stupid or incompetent to do.
Kids were being born smarter all the time when he came along, and they would be so forever more. He was about the last dumb kid ever born.
Even his mother had to admit that Albert was a slow child. What else can you call a boy who doesn't begin to talk till he is four years old, who won't learn to handle a spoon till he is six, who can't operate a doorknob till he is eight? What can you say about one who put his shoes on the wrong feet and walked in pain? And who had to be told to close his mouth after yawning?
Some things would always be beyond him—like whether it was the big hand or the little hand of the clock that told the hours. But this wasn't something serious. He never did care what time it was.
He invents machines to cheat in school:
Albert never learned to write a readable hand. To get by in school he cheated. From a bicycle speedometer, a midget motor, tiny eccentric cams, and batteries stolen from his grandfather's hearing aid, Albert made a machine to write for him. It was as small as a doodlebug and fitted onto a pen or pencil so that Albert could conceal it with his fingers. It formed the letters beautifully as Albert had set the cams to follow a copybook model. He triggered the different letters with keys no bigger than whiskers. Sure it was crooked, but what else can you do when you're too dumb to learn to write passably?
Albert couldn't figure at all. He had to make another machine to figure for him. It was a palm-of-the-hand thing that would add and subtract and multiply and divide. The next year when he was in the ninth grade they gave him algebra, and he had to devise a flipper to go on the end of his gadget to work quadratic and simultaneous equations. If it weren't for such cheating Albert wouldn't have gotten any marks at all in school.
Albert goes on to invent robots to do everything for him. In this excerpt he has to take a test without the help of his robots:
But he hadn't any of his gadgets or machines with him. He was on his own. He left half a dozen other proverb fill-ins blank. Then he saw a chance to recoup. Nobody is so dumb as not to know one answer if enough questions are asked.
'_________ is the mother of invention,' it said.
'Stupidity,' Albert wrote in his weird ragged hand. Then he sat back in triumph. 'I know that Eurema and her mother,' he snickered. 'Man, how I do know them!'
But they marked him wrong on that one too. He had missed every answer to every test. They began to fix him a ticket to a progressive booby hatch where he might learn to do something with his hands, his head being hopeless.
A couple of Albert's urbane machines came down and got him out of it. They explained that, while he was a drifter and a derelict, yet he was a rich drifter and derelict, and that he was even a man of some note.