The President of the ASTI is reminding Leaving and Junior Certificate students to get plenty of rest between exams.
Nearly 121,000 pupils will sit the tests over the coming weeks.
English will be the first subject to be examined for both sets of students, with the papers due to begin at 9:30 tomorrow morning.
Ger Curtin, President of the ASTI, is urging young people not to neglect their health over the next few weeks.
He said: "Eat well, sleep well, the one thing that keeps being forgotten is to get plenty of rest.
"Every day is a long day at Leaving Cert and it is also the first exam for junior cycle people so rest and put things in perspective."