How do I tell my parents that I failed a math test?

my parents and i have worked really hard to boost up my stupid math grades, but my *$#%@!&^ math teacher taught us all the stuff that would b on the test the last day, and told us it wouldn't be on that. well, my dad wasnt home that day and i failed the test. how do i tell them? weve been working sooooo hard, theyll b really pissed at me.