Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
Of all the schools that left before 2003, what is the average year joined?

### Inputs:
table_name: table, columns: ['School', 'Location', 'Mascot', 'County', 'Year Joined', 'Previous Conference', 'Year Left', 'Conference Joined']

### Response:
SELECT AVG Year Joined FROM table WHERE Year Left < 2003