I'm a 15 year old guy who's in grade 10 and I'm in love with my best friend who goes to a different school (however lives nearby) and is in grade nine (and single) should I ask her out or keep our friendship the way is it?

As long as she isn't already crazy about someone else, it should be pretty safe to ask her out. If your feeling nervous, sometimes it can help to find out how she feels about you before asking. When I was your age I used to be sneaky and get one of my buddies to do some fishing to find out if someone I liked, felt the same about me. But regardless of what you find out, you can never really be certain if a girl likes you until you ask! A good sign is how she reacts when you talk to other girls, if there is a hint of jealousy then you know she has feelings for you which is a good start.

I agree with LeanneDucan... if you like her and don't think she likes anyone go for it! But first, start to give her hints that you like her and see how she reacts to it.