Field trips by Kleenex. Parks by Sprite. Library books from dd's Discounts.

As kids head back to school, parents head back to fundraising, and savvy marketers see schools as an inviting opportunity to profit while doing good. Many recognize families' desire to help schools as an entree into a lucrative market.

Schools long have run fundraisers by reaping a portion of proceeds from gift wrap, candy or cookie dough sales, or by selling discount coupon books from local businesses.

Now one increasingly popular strategy focuses on marketing, not sales, through online contests. The pitch