Greenbush was originally formed in 1976 as Interlocal No. 609, and legally known as Southeast Kansas Education Service Center, with 9 counties in Southeast Kansas working together to provide educational opportunities that had previously been available only in larger urban areas. The agreement was unique in that no taxes were to be collected by or for the Interlocal and there was no overall membership fee. Instead, schools would pay only for the services they needed, ensuring programs would live or die based on their quality and efficacy.