I am not sure how long you consider a break is. But if you wish to drink water, wipe the sweat away, or take some deep breaths, then it should be fine.
But if you mean long breaks that allow you to sit down for 5 minutes, then it is unfeasible. Only diploma exams allow singing candidates incorporate a short break in the rundown.
DipABRSM, Singing
LMusTCL, AMusTCL, Music Theory and Literacy