The child has "a diagnosis of ADHD autism, and his anxiety around school and unmet needs there led to him being unable to leave the house", according to a statement on Central Bedfordshire Council's website.
Central Beds Council accepts it "didn't provide the boy with alternative education from March 2021, when it became aware he wasn't attending his school", said the statement.
A complaint from his mother to the council in August 2021 was investigated by an independent investigator and upheld.
"We've fully considered those findings and accept the conclusion that there were avoidable delays in providing education to the child," said Central Beds Council.
"We're truly sorry for the issues the family has experienced. We understand the impact it had on them and we've unreservedly apologised for this.
"It's important to be open and transparent about the complaint findings. So we've agreed with the investigator and the parent to publish an anonymised version of the report."
The statement reveals the local authority was notified in May 2021 by a neuropsychiatric consultant that the child had an autistic spectrum condition, demand avoidant behaviours and related extreme anxiety.
"This prevented him from accessing school on medical grounds. The capacity to respond proportionately during the child’s extended absence from school was hampered by the absence of medical evidence and explanation.
"Central Beds Council asked the parent to provide substantial evidence to explain why the child was unable to attend school because of medical issues.
"When she lodged the complaint, the mother reported her son missed out on his education for more than five months. She stayed at home to care for him, and the family have been caused avoidable distress and anxiety.
"Medical evidence of the extent of the child’s severe anxiety wasn't provided by parents to the school or Central Beds Council's access and inclusion service at the point of the child’s sustained absence.
"Central Beds Council wasn't in possession of all the information required to enable effective decision making regarding medical needs provision," added the statement.
"Consequently, the council identified that the child’s educational requirements didn't meet the criteria for medical needs at the time.
"We acknowledge we didn't listen adequately to the views of the parent and child in managing the difficulties he encountered attending school.
"Our approach was too reliant on the views of the child’s school and too focused on following strict process and criteria, rather than considering a holistic view of the child’s circumstances.
"Clinical evidence of the child’s needs was provided in May 2021, but we decided this was insufficient medical evidence to satisfy the Section 19 threshold under the Education Act 1996.
"Although the investigator confirmed that the Section 19 threshold hadn't been met in this case, we accept we should have considered the explanation of the child’s non-attendance where there was a medical reason and special educational needs.
"This should have triggered the council’s duty to arrange alternative provision immediately. As this didn't happen, the boy was unable to attend school and has missed a considerable amount of his education entitlement."