NY -- Standard & Poor's CreditWire 4/16/98 û- Standard & Poor's today assigned its triple-'B' underlying rating (SPUR) to Vista Unified School District, Calif.'s certificates of participation (1998 financing project) dated May 1, 1998 due May 1, 2023. The certificates are expected to receive a triple-'A' rating based on bond insurance. The rating reflects: -- The district's good general creditworthiness; -- An asset-transfer lease structure that includes the district's covenant to budget and appropriate lease rental payments; and -- Strong project essentiality - a middle school. Certificate proceeds will finance capital improvements to district facilities. The district's creditworthiness reflects: -- A stable local economy, -- Low debt offset by large and increasing capital needs, and -- Good financial operations offset