I agree that the parents should be told but it also sounds like the child is afraid of repercussions at home. I probably would have questioned him a little bit about why he thought he needed to hide the fact from his parents - maybe the punishment for an "accident" would be severe. At the same time that probably means he has developed a pattern of laziness at home that is now transferring to daycare too. Hard to know what is going on for both sides but he does need to tell the parent.