Table schema:
CREATE TABLE university (school_id VARCHAR); CREATE TABLE basketball_match (team_name VARCHAR, school_id VARCHAR); CREATE TABLE university (enrollment INTEGER)

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