Two well-respected companies that provide a variety of workbooks for 5th-grade students are Kumon and Spectrum. Both offer workbooks covering math, reading and writing skills, as well as some other more specialized topics.
Kumon is a company that operates popular tutoring centers throughout the United States. It also offers workbooks available to anyone for use at home. The teaching material in the workbooks follows the same "Kumon method" used in the tutoring centers.
Spectrum is a publisher that offers workbooks and educational materials that are widely used by teachers and parents. The materials are aligned with many state standards, as well as Common Core. They can be found online or at most local bookstores.