AUSTIN, Texas--(BUSINESS WIRE)--Fitch Ratings assigns an 'AAA' rating to the following Austin Independent School District, Texas' (Austin ISD or the district) unlimited tax bonds (ULTs): --$75 million ULT refunding bonds, series 2015A. The 'AAA' long-term rating on the bonds is based on a guaranty provided by the Texas Permanent School Fund (PSF), whose bond guaranty program is rated 'AAA' by Fitch. (For more information on the Texas PSF see 'Fitch Affirms Texas PSF Rating at 'AAA'; Outlook Sta