Mr Wood said the school was not fully fenced and was not a "fortress or prison" with teachers patrolling the boundaries.
"It's perfectly possible for a student to leave the school unnoticed."
He would not say how much the school knew about the parenting order, but only that they had been given some information when Michael was enrolled.
Mr Wood would also not say when Michael was noticed missing, except to say that day, the afternoon programme was different to normal.
There had been no investigation launched into how the situation was able to come about.
"It's nothing like a formal review, but we've reflected on our own processes and how the situation unfolded with respect to if there is any possible learning we can take from this."
He doubted there was anything the school could have done that would have been able to prevent someone who wanted to leave the school to leave.
Auckland University law Professor Warren Brookbanks said schools had an obligation to protect their students under the Education Act.
"If they know there is a parenting order in force, they should be at least alerted to that fact and doing what they can within the confines of the school to protect."
There was a possibility of civil or criminal legal implications, he said.
Police had been searching Curio Bay in Southland since car pieces washed up last week and today Inspector Kevin Lloyd confirmed a vehicle discovered late last week on the bottom of the bay was Mr Beckenridge's dark blue Volkswagen Touareg.
Mr Lloyd said police were still working on a process of how to retrieve Mr Beckenridge's vehicle from Curio Bay.
"Due to yesterday's search being unsuccessful in gaining any further information about what may be in the vehicle, police reiterate that the matter is still being treated as a missing persons enquiry and will be continuing to conduct inquiries into locating Mike and John."
Mr Beckenridge is also known as John Robert Lundh, Knut Goran Roland Lundh or John Bradford.
Any contact by him with Michael was a breach of a parenting order, Mr Lloyd said.
Michael is of solid build and of Asian descent. Mr Beckenridge is 1.75m in height, of medium build and of Swedish descent.
Anyone with information that might assist in locating the pair should contact the Southern District Command Centre on 03 471 5002. Information can also be provided anonymously to the organisation Crimestoppers on 0800 555 111.