Around 55,000 students began the Leaving Certificate examinations at centres throughout the country this morning.
A further 60,000 took their first Junior Certificate examination papers.
For the third year running, bonus CAO points for Higher Level Leaving Certificate Maths have led to a rise in the number of candidates opting for that paper.
Just over 30% of students hope to sit Higher Level, compared to 19% three years ago.
It is the highest number yet.
Last year's exam papers saw what the State Examinations Commission called an unacceptably high number of errors.
The SEC said it has taken on additional staff and put further control measures in place to try to avoid a repeat.
President Michael D Higgins and Minister for Education Ruairi Quinn wished all the students well.
In a statement, President Higgins said: "Over 115,000 students and families are involved in another important element of the education cycle.
"Students, in their differing circumstances, will have put their best efforts into their studies.
"With the support of family and teachers, they will now undertake their examinations with their best expectations."
Mr Quinn also reminded students that while the State exams are an important milestone, they are just one of a vast array of opportunities for education and training.