Today's honours maths paper was "battle" for the one in five students taking the subject at higher level.
The exam, which is due to be phased out by 2014, was described by one teacher as "one of the most challenging of recent times."
"Of the six most popular questions, three of them had elements that were exceptionally challenging," said Aidan Roantree of the Institute of Education in Dublin. "It was of little consolation that the other two questions that are generally less popular were accessible."
Question 7, on differential calculus, is chosen by most students each year. Today's version caused problems for many, according to reports.
"It needs to be said, this was the worst question on the paper," said Brigid Cleary of St Flannan's College in Ennis. "It featured three diagrams that the students would not be accustomed to at all. Some of my students didn't even attempt it. As one astutely noted, it was more like a question off a Project Maths paper."
Project Maths is the new maths syllabus currently being introduced at Leaving Cert. Just over 2000 students sat Project Maths exams at higher and ordinary level yesterday.
"Question 8, another popular option, also had some very difficult elements," said Brigid Cleary. "Overall, I think the students will be hoping for a better Paper II on Monday."
Almost 40,000 students took yesterday's ordinary level maths paper, which was described as "fair and very doable" by one teacher. "The paper gave weaker candidates the opportunity to demonstrate their mathematical skill," said Jean Kelly of the Institute of Education.
"Some tricky elements presented more capable candidates the chance to showcase their knowledge."
One teacher queried the focus on reciprocal functions in the last question, which she described as "unfair". "The question deviated from the usual structure and with its emphasis on a part of the course that not all students will have focused on, it left some stuck," said Bríd Griffin of Carlow Institute of Further Education.
"The real bogey on the paper, though, was the algebra question. Many of my students didn't like it at all."
Twenty four schools sat a partially revised Project Maths paper yesterday, and will sit a fully revised paper on Monday. By 2015 all schools will examine the Project Maths syllabus. It is hoped that the new course, with its focus on practical maths and subject context, will attract more students to higher level.
