It's almost anything out of the ordinary by definition, but usually refers to children somewhere on the Autism spectrum. They often struggle with being bullied in public school and depending on where they are on the spectrum can cause considerably increased workload for the school or even have outright behavioral problems complete with physical violence. That's extreme and rare thankfully, but even kids with relatively mild conditions can struggle in a chaotic public school environment.
Tiny suggestion: s/children/people. It's true that it's usually used to refer to children, but that's just because autism is most identifiable in early childhood. Autism (or Asperger's syndrome) is not something you can 'grow out of' or 'cure', because it's a difference in basic cognitive functions.
