Aspergers doesn't eventually go away

My 15 year old son has transferred from the private education system to the public education system this year. He was diagnosed with Aspergers Disorder when he was 4.He has followed the usual path for ASD attending early intervention and being funded through out school. His diagnosis was reconfirmed on the DSM -IV scale in 2004 when he started in the private education system.I have just been informed by the public school that they cannot apply for funding in the public education system unless his diagnosis is confirmed by a psychiatrist yet again. Whilst this can be easily be done and i have gone ahead and made an appointment I find it insulting that the beauracrats think the ASD is something that can be cured or will just go away. I have enough stress attending appointments and supporting my 3 ASD children. Why doesn't the government accept a diagnosis for the duration of the child's life?