Behavioural and emotional difficulties in students attending schools for children and adolescents with severe intellectual disability.

O'Reilly et al. (2000) visited schools for pupils with severe intellectual disability.

They gave teachers a short checklist that flags emotional and behaviour problems.

No extra tests or teaching happened; the team just counted how many kids scored above the clinical cut-off.

Half of the students passed the cut-off, meaning they show clinically significant behaviour or mood problems.

The strongest link was with physical disability: the more help a child needed to move, the more likely problem behaviours were noted.

The 50% rate is almost identical to the 52% later reported by Dworschak et al. (2016) in a much larger sample, giving the number staying power.

Chadwick et al. (2000) ran a similar survey the same year and also found daily-living skill deficits, not just physical disability, tied to problems like self-injury and sleep.

Myrbakk et al. (2008) went further, showing that many of these behaviour problems sit on top of hidden psychiatric disorders such as depression, so the checklist score may signal a treatable illness, not just "severe ID behaviour."

Beqiraj et al. (2022) updated the picture: when children have pro-social skills and mothers report low stress, challenging behaviours drop even in the same special-ed setting.

If you work in a school or centre for severe ID, plan for one in two clients to need a behaviour or mental-health plan.

Use the simple teacher checklist first; it takes minutes and picks up the same half the class that later studies keep finding.

When the score is high, look past the label: check for sleep issues, pain, depression, parent stress, and missing daily-living skills, then build those into the behaviour plan instead of treating only the topographies you see.