user: Question: What is the average enrollment 08=09, for the team that had a previous conference of Lake and IHSAA class of 3A?
Columns: ['School', 'City', 'Team Name', 'Enrollment 08-09', 'IHSAA Class', 'County', 'Year Joined', 'Previous Counference']
Types: ['text', 'text', 'text', 'real', 'text', 'text', 'text', 'text']
Sample row: ['Hammond Bishop Noll', 'Hammond', 'Warriors', 453.0, '2A', '45 Lake', '2007', 'Lake']
SQL:

assistant: SELECT AVG("Enrollment 08-09") FROM "Table" WHERE "Previous Counference" = 'Lake' AND "IHSAA Class" = '3A';