Depressed due to being Bi

So I'm slowly becoming Bi and my parents have always told me that when I'm older I have to marry a man... I'm only in grade 7 and everyone just seems to hate people that are gay, Bi, Pan or A and so I wanted to come out to my best friend but... I know I'll be judge... I go to a catholic high school and... They'll expelle me for being Bi... Any advice???