And if that does not kill off their love of learning, nothing will.
No, my son passed the 11+ after being forced by us to put in the effort over the Summer, and is loving his grammar school years. He's constantly challenging himself and after a bit of a shaky/haphazard start due to transition, is now in the top 15 of his year (out of 150) and still aiming higher. He's a happy, well adjusted 15 year old, with lots of friends and outside activities. Certainly not a "swot" who does nothing else! We have no regrets and DS has since said that he's glad we pushed him.
By contrast, I had a miserable existence in my state comp and hated the place and was suicidal due to horrendous bullying, physical abuse, and went from a straight A pupil at primary to a complete failure at 15 (only 1 O level), all due to crap school, with crap teachers.
At the end of the day, stereotyping simply doesn't work. Grammars are fine for many, just as comps are fine for many. Some boys are lazy, just as some girls are.