Sorties de salle

08:41 Jun 6, 2016 

"tiers temps" means special medical or physical condition as Nikki explained
A diabetic student may need time for blood analysis, insulin injection and so on.
Also the time needed to go to the loo with an arnchair may be much longer if the restrooms close to the room are not accessible
So as Nikki and cchat explained, the time out of the examination room is counted and added to the length allowed

02:04 Jun 6, 2016 

I have worked invigilating exams for the baccalauréat. "Ordinary" students can leave the examination room to go to the loo. They are accompanied. (This surprised me, as in the UK, this was simply not allowed). It's silly really as you can imagine that all sorts of cheating are possible. We didn't actually watch them pee!
If this is all about students who are entitled to a "tiers temps", then with 4 years' experience as an AVS, I have accompanied students in official baccalauréat exams. For example, if my memory serves me right, the ES exam is 4 hours long and if the student has opted for Sciences Politiques as an extra speciality, then the exam is 5 hours long. The 1/3 temps adds 1 hour 40 minutes to the examination. Considering that these students are often likely to tire more easily, it is a real achievement! I accompanied a partially sighted girl through this exam; quite a feat for her, I can tell you! Yes, she was allowed to leave the room, take a break to eat etc and the time taken out was counted so that she could have the full 6h nd 40 minutes examination time.
"ordinary" students who have a pause-pipi do not have their time counted and added on.

10:36 Jun 5, 2016 

totally agree with cchat. 'Leaving the examination room' would usually imply something like a bathroom break, with the candidate coming back. In the link I quoted in my agree to Charles, one notices that it is (in English) the 'not coming back' that needs to be made explicit.
If I might be even more pedantic, leaving the exam room to go to the toilet is not exactly the same (even physically)as permanently leaving the exam room. In the case of a definitive exit, you have to give in your exam paper.
cchat is quite right to point out that what is important in the instruction here (not in the translation question posed) is the fact that the time you spend at the toilet if you are a beneficiary of "tiers temps" is not counted.

07:23 Jun 5, 2016 

These are the special conditions that apply to candidates with some forms of disability. As the reference I posted shows, all candidates may leave the room after the first hour (for bathroom breaks), but they don't get that time back. "Tiers temps" candidates may leave the room, and the clock stops for them during their break. They are already allowed one third more time for the exam, to make the situation more equitable for them.

20:39 Jun 4, 2016 

These are special rules for candidates with some form of disability.
"Tiers temps" means extra time for the exam, i.e. 20 minutes extra per hour. Such candidates are also allowed to leave the room for breaks and they get that amount of time back. If they are out for 10 minutes, they get 10 minutes back. Other candidates may leave the room (after the first hour) but they don't get any time back.