They say he is uncontrollable. The child was suspended for the assault. After sleeping in for a few days, he is back in school making other people's lives miserable. Let's suppose, for the sake of argument, that this child is sufficiently rational to understand the connection between his behavior and punishment. Let's further suppose that the Singapore solution is the only sanction that impresses him.
Suspension is the worst that customarily happens to school predators.
For tough kids that sanction is a joke, just time off to run the streets. So, having had the Singapore solution forbidden by people who escape the price of its banning, school officials command few if any sanctions that impress hooligans. Sure, the Singapore solution might damage children thus corrected. It also could encourage them to think that might makes right or that violence is the best way to resolve conflicts. If children are having trouble at home, if they are unsafe on the streets, if their lives outside of school are chaotic, they at least should be able to experience something positive in school.