I agree with Bear. Know what your market will bear. At a school fundraiser people aren't going to pay high, boutique range prices. You have to keep the prices low-make simple products like pot holders, placemats, small table squares. You're probably not going to sell anything for over $15.00 no matter how beautiful and hand made your work is.
Know your demographic-my area is really depressed and people wouldn't even buy a $5.00 pot holder--they can't. It's different raising money at a school craft fair than at a community craft fair. Just my humble opinion from what I've experienced in my neighborhood.