When 11-year-old Milly and her mum Jenny arrived at the school principal's office, Jenny's heart sank.

There were more people there this time than usual — and she knew this would be a problem for her daughter.

They were there for Milly's re-entry into school after yet another suspension.

And it didn't take long.

Within half an hour, Jenny had sustained punches, the office was trashed, and the police were on the way.

Milly stood, amid the chaos, on the principal's desk.

Jenny would later discover she was dealing with Pathological Demand Avoidance (PDA).

PDA is described as an atypical profile of autism.

It's defined in the Australian government's National Autism Strategy, released earlier this year, as:

"An extreme need for control and autonomy driven by high levels of anxiety or a

See Full Page