Contact your local Borders Bookstore. The store in my area is going to have a gift wrap area that they are staffing with individuals and groups. The proceeds will go to your school. You can gather some other Moms and Dads and wrap gifts and fundraise for your school in your Teacher(s) honor as their gift.
Also check out www.seva.org
You can give a "Gift of Service" for $30 you can help fund "Enrichment activities for a Native American Youth" or $25 to provide "Eye care for one Girl or Women" in developing countries. The gift recipient dosen't know the amount you've spent and you can make it a group gift to all of your childrens teachers. (Either request more gift cards or copy them yourself)
Another favorite of mine is "The Womens Bean Project"
"Since 1989 we have been helping women break the cycle of poverty and unemployment"
They sell bean soup mixes, cornbread mix, salsa and dip seasoning mixes, and many other items. Their bean soup mixes are $5.25 and $5.75 Their spice rubs are $3.00
And when we were kids my Mom would bring us to the local grocery store that sold flowers and we would get our teachers a bouquet of 2 or 3 red Carnations and we would make a card. Our teachers always LOVED them. Just picture your child walking in to class with flowers and a homemade card for their teacher.