...S&P Global Ratings assigned its '##' long-term rating on Platte County R-III School District, Mo.'s $73 million series 2021 general obligation (GO) school building bonds. At the same time, we affirmed our '##' rating on the district's existing GO bonds and our '##-' rating on the district's existing leasehold revenue bonds. The outlook is stable. The series 2021 GO bonds are secured by the district's unlimited-tax GO pledge. Voters authorized the bonds pursuant to an election held within the district on April 6, 2021. Proceeds from the bonds will be used for constructing a new middle school, renovating an elementary and high school, and installing safety and security improvements in district facilities. Based on our application of "Issue Credit Ratings Linked to U.S. Public Finance Obligors' Creditworthiness" criteria, published Nov. 20, 2019, we rate the existing leasehold revenue bonds is one notch below the GO debt ratings because of annual appropriation risk....