"Umbrella schools come in many different shapes and sizes. Many offer a wide range of services to a homeschooling family. Umbrella schools may allow homeschoolers to participate in sports and/or labs, offer annual testing, guidance counseling and more. Some umbrella schools may only serve as a record keeping office for a homeschooling family’s records.
Umbrella schools may dictate the type of curriculum which homeschoolers must use, while others may leave the choice up to the individual families. Some umbrella schools are only offered to families of specific faiths, while others are more flexible with their enrollment guidelines." http://www.mamashealth.com/homeschool/umbrella.asp