Six Flags Fiesta Tickets are on sale! The 1-Day ticket can be purchased at Oak Hills Terrace Front Office with Mary Leija. The cost for the 1-Day ticket is $35.00, CASH ONLY! The 1-Day ticket will be sold Monday - Friday from 8 am to 3 pm at the front office. The Six Flags Ticket sales benefit the Northside Education Foundation which provides grants to NISD teachers for innovative programs.