The CAO is to review its operations and procedures after it was widely criticised this week.
Yesterday, both the Minister for Education, Mary Hanafin, and the ASTI were sharply critical of the CAO's approach to students.
Thousands of students and their parents were distressed earlier this week, as the CAO computer system struggled to cope with applications in advance of yesterday's 5.15pm deadline.
The CAO has strongly defended its operations publicly but yesterday Ms Hanafin said it should have been more sympathetic to the plight of thousands of students.
Yesterday, the chairman of the CAO, David Redmond, the registrar of NUI Maynooth, acknowledged that the service to students was not what the CAO would have wanted.
The CAO, he said, would be reviewing its operations to ensure there was no repetition.
However, he said the decision not to to extend the deadline for applications beyond yesterday had been vindicated.
The CAO said it was unable to extend the deadline because of its contractual obligation to those who had applied in time.
In all, the CAO has taken 51,500 applications online. Just 2,400 applicants applied online yesterday, compared to 7,800 on Wednesday when online users experienced severe difficulties.
Yesterday, Ms Hanafin encouraged the CAO to review its procedures. "I think the whole thing would need to be reviewed, maybe to encourage people to apply in different stages, earlier and so on. But it's a lesson I think for the CAO because the last thing that Leaving Cert students need is more stress."
Last night, John White, general secretary of the ASTI, called on the CAO to "review its mechanisms to ensure that the stress caused to parents and pupils this year does not recur".
It is vital, he said, that the CAO retains the confidence of the whole community. "ASTI suggests that the CAO publicises to schools that applications can be submitted well in advance of the final deadline. "
Ms Hanafin said the run-up to the CAO deadline was a very stressful time for students.
"We all leave things to the last minute. That's what everybody does, and I know that there are students who are still trying to make up their minds about the direction that they want to go in. So I'm very sorry that this is adding to the stress for them. Unfortunately, despite my request, the CAO are saying that they just legally cannot extend the deadline . . . They're basing their answer to me on legal advice."