Let's imagine an amazing technology that could teach just about anything, but will it eliminate inequities in education? Wealthy parents will get the best hardware for their own children, while the children of poor households will have access to older models in need of repair. Rich kids will easily learn quantum physics. Poor kids might come out quacking like a duck.
In the above quote, what does "Poor kids might come out quacking like a duck" mean?
It means pretty much exactly what it sounds like: that the poor-quality devices that the poorer families could afford could have nasty side-effects from the general technology in use. These side effects could (hypothetically) be as bad as affecting their brains in such a way as to make them quack the way ducks do.
It's a bit of rhetorical hyperbole, but in principle it's not really impossible to rule that idea out for an invention that's acting on the mind so intricately.
