text: Reuben Lewis from Llanidloes was driven 45 minutes from Ysgol Cedewain, Newtown, without teachers or transport staff realising he was still on board.
  BBC Wales understands he was then left alone on the parked bus in Rhayader on two separate occasions.
  Powys council said there had been a "serious breakdown in communication".
  A spokesman added it had spoken to the school and all contractors to ensure immediate safeguards were put in place to prevent any similar incidents in future.
  The most recent incident was on Monday, when it was only noticed Reuben was missing after his sister spotted he was not present at a school swimming lesson she was teaching at Maldwyn Leisure Centre in Newtown.
  Police were told and Reuben was found at the Simon Price Cars bus depot.
  Reuben's father, Rob Lewis, said there had been "several mistakes" by the school and transport provider in the past year.
  He said Reuben was left on the bus in May last year and left at school the following December.
  "I was in total and utter shock that this had happened again," he said.
  "I'm always happy to give someone a second chance, but now I wish I'd never given them a first chance. This beggars belief.
  "It was sheer luck that it was noticed Reuben was missing on Monday because his older sister works part time as a lifeguard in the leisure centre.
  "She knew her brother was meant to be at the swimming lessons and when she couldn't see him she rang her mother and we alerted the school and the police."
  Mr Lewis said he had an agreement with the school to notify them before 09:00 if Reuben would not be attending, so the alarm would be raised if he was not there.
  "So how could this happen again on Monday, after we were given so many reassurances?" he added.
  Simon Price, owner of Simon Price Cars, said the company was contractually unable to comment while the investigation was ongoing.
  A council spokesman added: "Although we have undertaken an internal review of the circumstances surrounding this incident we have advised the parents to make a formal complaint so that we can investigate all of the circumstances in the fullest detail as a matter of urgency.
  "We have apologised to the parents."
target: An investigation is being launched after a 10-year-old deaf boy who has autism was twice left on a school minibus and driven back to the depot.