A warning has been issued to the government after Surrey County council was ordered to pay £1,000 over delays to education support.
The Local Government Ombudsman said a plan for a girl with autism was delayed by nine months, "mainly" due to a lack of educational psychologists.
It said "significant input" was needed to resolve a national shortage.
The council apologised for the "distress" the family experienced and said it would take "necessary action".
The Department for Education has been approached for a response.
The watchdog said the council had agreed to carry out an education, health and care (EHC) assessment for the girl, which would detail what support needed to be put in place.
She had been been "struggling to cope" in a mainstream school, the ombudsman said.
But a plan for her education support was issued in September 2023, nine months over the legal timeframe for completion.
It meant she was unable to attend school for months.
Advice from educational psychologists is needed to complete EHC assessments, but half of Surrey's posts are vacant.
