Freerice is a non-profit website that is owned by and supports the United Nations World Food Programme. Freerice's mission is to provide education to everyone for free and to help end world hunger by providing rice to hungry people for free.
To use the program, students log in and select their subject area: Humanities, English, Math, Chemistry, Language Learning, Geography, Sciences, and Test Preparation. For every question a student answers correctly, Freerice donates rice to those in need.
We have personally used this website. My boys enjoy doing it knowing that they are getting school work done while also helping someone else. It does not include any instruction, but it does offer some good practice activities.