Help with teacher &*phone?

During the big test at the end of the year.. called MCAS.. im always done like 2 hours before we end and i just sit there. we cant get up talk or do anything but sometimes they let you use your phone.. but my teacher wont. so tommorow when i ask and say "cann i use my phone when im done" and he says "no".. what should i say? hes a science teacher so he will have a smart *** remark... !?! thanks