Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE basketball_match ( team_name VARCHAR, school_id VARCHAR )
TABLE: CREATE TABLE university ( school_id VARCHAR )

### Question ###
Find the team names of the universities whose enrollments are smaller than the average enrollment size.

### Accurate SQL ###

SELECT t2.team_name FROM university AS t1 JOIN basketball_match AS t2 ON t1.school_id = t2.school_id WHERE enrollment < (SELECT AVG(enrollment) FROM university)