Individuals can not earn at this time with them. Under their FAQ
they have this
Is my school currently enrolled in Box Tops for Education?
Over 90,000 K-8 schools are enrolled in the Box Tops program. To find out if your school participates, click the Join Us link on the home page.
The Box Tops for Education program is available to any accredited public, private or parochial school, for grades K-8, in the United States that is organized and primarily operated for educational purposes; U.S. military schools, K-8, worldwide; and accredited home school associations, K-8, in the United Sates that are organized and operated primarily for educational purposes and have 15 or more students.
I also know HS families that collect them and then sell them on ebay or craigslist for close to what they would get if they could send them in.