Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_name_63 (year_joined VARCHAR, enrollment VARCHAR, ihsaa_class VARCHAR)
### Question:
What year joined had an enrollment less than 438 and an AA as the IHSAA Class?
### Answer:
SELECT year_joined FROM table_name_63 WHERE enrollment < 438 AND ihsaa_class = "aa"