...S&P Global Ratings lowered its rating on Advanced Technology Academy (ATA), Mich.'s series 2008 revenue bonds to '##' from '##+'. The outlook is stable. We lowered the rating based on the 'U.S. Not-for-Profit Charter School Methodology,' published on Jan. 3, 2017, on RatingsDirect. We assessed ATA's enterprise profile as adequate, characterized by a generally stable demand profile with flat enrollment, a limited waitlist, academics that compare well locally, and a solid charter standing. We assessed ATA's financial profile as vulnerable, with an extremely weak liquidity profile which is partly offset by good coverage levels and a relatively manageable debt burden. We believe that, combined, these credit factors lead to an indicative stand-alone credit profile of '##' and a final rating of '##'. In our opinion, the '##' rating on the bonds further reflects the risks associated with the school's very low liquidity and continued reliance on short-term borrowing. The '##' rating reflects our...