It's a bit lazy, and i can't imagine incredibly worthwhile as it just pisses off the good kids and makes them less inclined to try hard, and the naughty kids aren't often that bothered about merit points anyway - especially when they're all being punished equally.
What's with the argument that only people who have actually taught children of that age can really judge? Does that mean all non teachers should butt right out of their childrens education and not question anything, even if they think its crap practice? anyone with a child is qualified to judge how effective, fair, useful, damaging, rubbish, brilliant the way their child is treated. They might not be able to change it, but if its particularly rubbish they have the job of undoing and counteracting it at home.