user: Question: What year joined had an enrollment less than 438 and an AA as the IHSAA Class?
Columns: ['School', 'Location', 'Mascot', 'Enrollment', 'IHSAA Class', '# / County', 'Year Joined', 'Previous Conference']
Types: ['text', 'text', 'text', 'real', 'text', 'text', 'real', 'text']
Sample row: ['Angola Community', 'Angola', 'Hornets', 911.0, 'AAA (AAAA)', '76 Steuben', 1989.0, 'Northeastern Indiana']
SQL:

assistant: SELECT "Year Joined" FROM "Table" WHERE "Enrollment" < 438.0 AND "IHSAA Class" = 'AA';