Honesty is not always the best policy. I observe this from some students I have. A student of mine in the past wrote to me in the beginning of a semester, "My father surprised me and my brother with a trip to Hawaii as our Christmas gift and I will not be returning to Iowa until late in the evening on Friday." He wanted to be excused for a week because his family planned to have a leisure trip to Hawaii. What a surprise, indeed.
He probably thought that by telling me the truth, he'd followed the suggested conventional wisdom. No, what he really reveled was his arrogance: I am going to have fun during the school time and I don't mind telling you that. Why? Just because I can.
Show some respect for the educator and the education you pay good money for. At least come up with some white lies, if you really want to be excused.