My eldest son is currently undergoing behavioural assistance & is being assessed for an autism related condition. He currently shares a room with his baby brother, but he can be so volatile sometimes that I'm afraid he'll hurt him. The behaviourist is in complete agreement that he needs his own room, but without a definate diagnosis I'm still liable for the tax if I upgrade to a 3 bedroom house. Is there anything I can do in meantime to fight my case?