Using interviews, observation, and archival documents, researchers traced the 4-year history of a "freestanding" interorganizational arrangement for school improvement in Santa Clara County (California). Called the "AB 65 Elementary Consortium," the interdistrict collaboration was started in response to California Assembly Bill (AB) 65, which mandates tests of elementary students' basic skills proficiencies. The proficiency testing consortium was "freestanding" in that member organizations contributed all the resources required. Established in 1977, the consortium began developing guidelines for proficiency tests, had a setback in early 1979 when its first tests (prepared by consultants) proved to be of poor quality, but retrenched and succeeded in publishing its own testing products in 1980-81. The tests chiefly measured math, reading, and writing competencies in grades 4, 6, and 8. Consortium membership grew from 12 districts and agencies in 1978 to 33 in 1980 and fell back to 25 in mid-1981. Important in the consortium's development were its sources and uses of services and information, the role of the Santa Clara County Superintendent of Schools, and the districts' local control over their own participation. An appendix provides data on the consortium and documents relating to its formation and products. (RW)