This year's Higher Level Maths Paper 1 has been described as 'very difficult' by a Maths teacher who is subject spokesperson for the ASTI.
Students were required to answer six out of eight questions.
Brigid Cleary of St Flannan's College in Ennis, Co Clare, described questions four and six as 'difficult'.
She said students were thrown by the use of graphs in question seven, which they would not have expected.
She said part of question eight was also difficult, as was a small part of question one.
The exam ended at 4.30pm.
The State Examinations Commission said its chief examiner in mathematics was satisfied that the questions asked on today's paper are within the parameters of the syllabus.
In a statement, it said it can confirm that Question 7(b) was correct, and that the material in Question 8(c) was within the syllabus.
In what appeared to be an attempt to reassure anxious students, the statement went on to say that observations on exams are reviewed when the marking scheme for that particular subject is being drawn up.
The SEC response came after students and some teachers criticised what they believed to be a very difficult Higher Level Maths paper.
The SEC said it had a well-tried methodology in place to deal with issues that arise in the course of the examination process.