Standard&Poor's Ratings Services affirmed its 'BBB-' long-term rating on Advanced Tech Academy (ATA), Mich.'s series 2008 revenue bonds. The outlook is stable. The rating affirmation reflects our view of ATA's good enrollment growth and historically adequate maximum annual debt service (MADS) coverage. ATA's operating margins have diminished during the past few fiscal years, and the school is budgeting for a loss in fiscal 2014 due to start-up costs of new classrooms. While we consider the weaker budget to be a credit risk, we anticipate that based on the budget, ATA will still generate adequate MADS coverage and will at least maintain its current levels of unrestricted liquidity. The 'BBB-' rating reflects our view of the school's: Healthy historical