> Young children or adults with severe behavioural problems are managed without antipsychotics and sedatives...

Indeed! In practice, they're often managed with dangerous restraint techniques, or mentally abusive solitary confinement practices! Consider, for instance, this wonderful coverage of Illinois:

https://features.propublica.org/illinois-seclusion-rooms/sch...

https://www.propublica.org/article/illinois-school-restraint...