Especially in middle grades, students are just passed the lower-elementary years in which they decorated heart shaped cookies and made their own Valentine Mailboxes but still bringing in their own Valentines and wishing they could have a party too.
I have done this experiment year after year and it is effective in that it keeps students engaged and focused on a day when all they really want to do is eat candy. They don't even really realize they are doing science and math and accept it as part of the special day. Students have so many questions about the body and in particular their heart and this is a great platform to talk about it!
-Student Anatomically Correct Coloring Sheet
-Teacher Notes on Heart
-Graphing and Response Question Sheet
-Scientifically Correct Valentines with facts on them