How do i kiss him unexpectedly ?

Today is the last day that i get to see the guy i like that likes me until graduation next week and then after that not until NEXT YEAR! Yesterday he tried to kiss me but my teacher is so annoying and he was standing right in front of us. So i turned my head, and i think he got embarrassed. SOO today i wanted to kiss him unexpectedly today in class when finals are over and we have free time. So can you help me out? I will be happy to answer your question in return :)