ODFOD.
As @Greensleeves has so eloquently said, "many secondary schools are increasingly hostile environments for neurodivergent children; rigid off-the-shelf behaviour policies, poor pastoral support, inadequate action around bullying, narrow and intolerant attitudes towards anyone who doesn't easily conform or has a different learning style."
But yeah, the reason the youngest child in the family isn't going to school is because they're copying an older sibling.
It sounds like the other older sibling, who doesn't appear to be autistic, is going to school no problem?
Could it possibly be that the younger child, who is also autistic, is also finding school intolerable and thus cannot attend?
They're not taking the piss, kids just want to be normal and go to school like everyone else. When they can't, it's heartbreaking. And it's CAN'T, not won't. It's not some stupid learned behaviour.
Mainstream schools can feel more like prison camps to many neurodivergent children. And yet we're surprised and blame the parents for not being strict enough when they can no longer force their children to attend?
If you had a job where your employer had rigid control of you all day, you were forced to obey every command or face the consequences, you didn't have control over your own appearance or even have control over when to use the goddamn toilet, would you think that was fine? Would you cope with a complete loss of autonomy all day, every day? This is what kids face in mainstream high schools now. Of course some don't respond well - especially autistic kids with a PDA profile.
Adult in a job that's destroying their mental health? Get signed off sick, find a new job that doesn't make them ill.
Kid in a school that's destroying their mental health? Come on parents, do your job properly and force them to go regardless.
Believe it or not, those of us parenting children with extreme school-based trauma got here because we DID do as we were told for many years. We forced them in: via bribery, threats of punishment, even physical force. And we all lived an increasingly miserable existence. Until one day the kid was just too big to actually carry in kicking and screaming, and then something had to change.
Being told they're copying someone else, or we just need to 'not give them the option', literally boils my piss.