...S&P Global Ratings assigned its 'A+' long-term rating to Vista Unified School District, Calif.'s estimated $31 million 2020 general obligation (GO) refunding bonds. At the same time, S&P Global Ratings affirmed its 'A+' long-term rating and underlying rating (SPUR) on the district's GO bonds outstanding, as well as its 'A' long-term rating and SPUR on the district's outstanding certificates of participation (COPs). The outlook is negative. Unlimited ad valorem taxes levied on taxable property within the district secure the GO bonds. The board of supervisors of the county has the power and obligation to levy these taxes at the request of the district for the bonds' repayment. The county is required to deposit such taxes, when collected, into the bonds' debt service fund. The district plans to apply the proceeds from its 2020 GO refunding bonds to refund a portion of its series 2012 GO refunding bonds. The district's COPs represent an interest in lease payments it makes, as lessee, for the...