"In some cases, it was used as more routine behaviour management practice,'' she said.
"With that in mind we have implemented a series of actions to improve Miramar Central's performance in all future dealings with challenging behaviour."
Read more: Minister reveals eight seclusion rooms being used in special schools
The ministry said the action plan was of the same level as a statutory intervention, but because of the school's level of co-operation it had been decided that a more formal statutory intervention will not be required.
Among the actions is that ministry staff will now be onsite to review all behaviour management plans.
Parents will also be asked to sign off on their children's behaviour management plans.
The ministry is now focusing on cracking down on other schools that have used seclusion rooms in the last 12 months.
The message is that all schools must stop using such rooms immediately and that Ministry of Education staff will be offering help to come up with techniques to manage students with extreme behaviour.
The names of the schools thought to have seclusion rooms have not been released.
"These schools will need to talk to their parents and communities and will be encouraged to do this as soon as possible.
"All schools need to understand seclusion is unacceptable. This case highlights that we should have acted much more decisively when we first received the complaint about the use of seclusion at Miramar.
"We know that there are health and safety risks around putting a child in a locked room. When a child is exhibiting extreme behaviour there are sometimes also health and safety risks to the child and other people."
Casey also apologised to the Education Minister Hekia Parata for the handling of the situation when it was made known to the ministry.
"It is clear that the ministry didn't act with the urgency it should have to stop the use of seclusion," Casey said.
"Children's wellbeing must be at the forefront of everything we do and we will work with schools and their communities to ensure we all get this right.
"We have also apologised to Minister Parata for the handling of the complaint and for a delay in informing her that the investigation had been completed."
Among the points in the Miramar action plan are:
• The New Zealand Schools Trustees Association will work with the board to provide guidance;
• The Positive Behaviour for Learning programme will be implemented into the school;
• A project manager will oversee the action plan and be accountable to ensure change.
The ministry said it would also look into regulatory and legislative implications of the Miramar case, as well as any potential legal matters that may surface in light of the situation.
Meanwhile, the Education Review Office has also been advised that they must always question schools about its strategies to address the needs of students with special needs.
Teachers working with children in special needs units must also be observed as part of ERO review processes.
Education officials first launched their investigation into seclusion at the Miramar school after a behaviour therapist found a 11-year-old disabled boy alone and distraught in the cupboard-sized room, with no way to get out.
The boy, who is autistic with the mental age of a toddler, was one of at least 10 children - mainstream and special needs - put in the "time out" room within the past year, largely without parent knowledge or consent.
While the use of the room was not illegal, it was "outmoded", the investigation found.
After the Weekend Herald broke the story, the Chief Ombudsman said it would investigate the use of seclusion rooms in schools.
Seclusion and time-out: they're not the same
The NZ College of Clinical Psychologists, which has more than 900 members, said it was important for schools to understand the difference between seclusion and time-out - which was a proven and good way of safely managing a child's behaviour.
Seclusion was totally different to the time-out method.
"Seclusion is where a person is placed in isolation from others in a room or area from which they cannot freely exit.
"The college does not support or approve the use of seclusion, as it can have negative impacts on the person's well-being and undermines their basic human rights.''
Time-out was defined as a method that required a specific plan and practise so that both teachers and students alike knew exactly what to expect - that children could use this time-out to regulate their emotions.
It should be in a place that is deemed to be a safe and predictable environment. It should be a comfortable place and with a familiar adult supervising nearby.
"Time-out is where, in a planned way, a child is verbally prompted or gently guided away from a situation for a period of time so that they can calm down.
"It's the removal of stimulation (such as loud noise) and reinforcers, such as attention.
"It is not a punishment."
The college stressed that even time-out should only be used for cases of "severe behaviour'' - for example, where the well-being and safety of other children or staff were put at risk and other strategies were not working.
