Home school curricula, such as AmblesideOnline.com and AllIneOneHomeschool.com, offer free resources for the sixth grade. Websites such as IXL.com and AdaptedMind.com feature free online resources for the sixth grade.
AmblesideOnline.com offers a free home school curriculum that includes recommendations for books available through the library. The site also includes links to online books suitable for the sixth grade. AllIneOneHomeschool.com is another complete home school system with free resources for all grade levels.
AdaptedMind.com offers free online resources for math and reading. Each free lesson includes activities, explanations and an instructional video. IXL.com offers similar resources. Both charge a fee for full access, but it's possible to use sample lessons for free.