Can I miss the last day of summer classes?

<p>I have a question. Does it really matter if I miss the last day of summer school for HEOP?? </-- didn't realize that it ended the 13th instead of the 12th and my mother had booked a flight thinking i wasnt going to NYU... but i AM going so I'll be staying this summer... then she changed the date to the 12th because the website said that it ended the 12th.... and now she wont reschedule the flight because it's so expensive. So, is the last day of summer school very important? Can i miss it??</p>