The school which excluded a pregnant teenager from enrolling was the subject of an audit by the Data Protection Commissioner following a complaint.
The college, which is not being named by The Irish Times, is cited in the commissioner's report published yesterday, but no further details are given.
The school is also being investigated by the Department of Education following a complaint by Children's Ombudsman Emily Logan.
The private school was subject to an unannounced inspection in February and a second inspection will take place next month, the Department of Education has said.
Several organisations involved in the post-primary sector have said the exclusion of the teenager because she is pregnant is highly unusual.
National Association of Principals and Deputy Principals chief executive Clive Byrne said principals should think about how they would want their own children to be treated.
"It is the norm that schools routinely deal with issues like this is in a supportive way that cares for the student without condoning the actions," he said.
"That is the type of ethos we would like to see in schools. The reaction of this school was not the norm.
"If you are a principal, the best way to deal with it is to think about how your own child would be treated. That is a pretty level-headed way," he said.
Ferdia Kelly of the Joint Managerial Body (JMB), which represents the management of almost 400 voluntary secondary schools, said pregnancy should "never been an issue" in relation to school admissions.
He said the school in question acted "inappropriately" in excluding the girl who was 16 at the time.
"The unfortunate side-effect of this issue is that there is an implication that schools are not supportive of pupils that are pregnant. Schools are highly supportive and pastoral towards girls who find themselves pregnant. There is never a question of their position in the school coming into question."
Ms Logan said the school did not appear to have a written admissions policy.
Mr Kelly said it was also a requirement of every school to have a written admissions policy, according to the Education Act 1998 which states: "The board shall publish, in such manner as the board with the agreement of the patron considers appropriate, a policy of the school concerning admission to and participation in the school."
The school in question which is privately run by an individual, has no board of management.
In a report published on the Children's Ombudsman website, Ms Logan said the girl in question tried unsuccessfully twice to enrol in the school, once when she was pregnant in 2009 and secondly after she had the baby in 2010.
When her mother wrote to the school principal, he replied: "Your letter surprises me. A neighbour called at your request and stated that your daughter was pregnant. I was shocked and I told her that I did not take in such girls."
Ms Logan wrote to the school in July last year following a complaint from the girl's mother.
She requested that the school furnish a copy of its admissions policies and complaints procedures, along with outlining its board of management structure.
In response, the school manager wrote to her: "Neither am I obliged to have any other frills that you mention. This school is NOT a haven for young pregnant people or for young mothers who, in particular, have been in two other post-primary schools. The school has an uncompromising ethos and will not become a dumping ground for those rejected elsewhere."
The girl had attended two previous secondary schools, first changing schools in October 2008 "as she was unhappy in that school", and "did not settle" in the second school. She then worked for a short period.
In 2009 she discovered she was pregnant and "made a decision that she wanted to return to school" and wanted to go to the school at the centre of Ms Logan's investigation as she had friends there.
Ms Logan said she could not see any evidence of an admissions policy and the school did not appear to have a complaints mechanism.
A spokeswoman for the Association of Secondary School Teachers of Ireland (ASTI) said there appeared to be a lack of accountability at the school and the case illustrated the need to have a board of management in every school.
"Clearly the school's failure to respond means they think this is going to go away. Lessons will have to be learned from this," she said.
The ASTI said every school should have an "open and transparent admissions policy which is inclusive, which actively promotes equality of access, and which is fully compliant with legislation.
"The vast majority of second-level schools are inclusive and seek to provide a supportive environment for students, regardless of their life circumstances."
Treoir, the teenage parents support programme, said it was "horrified" by attitudes towards the young mother by the school.
The Central Statistics Office (CSO) figures for 2009 found that there were 1,201 births to teenagers who were18 years or under and 161 were 16 at the time.
Margaret Morris, the national co-ordinator of the Teen Parents Support Programme, estimated that there are approximately 700 teenage pregnancies among girls of a school-going age.
She said most schools were supportive. "It is not acceptable that any school would not be supportive".
Some teenage girls are subject to discrimination, but it is less overt than in the case of the school in question and there are cases where such girls are made to feel "uncomfortable" in school, she maintained.
The Teen Parents Support Programme has developed guidelines for supporting students who are pregnant and those who are parents within the educational system.
Attempts to contact the school today were unsuccessful.