An existing database (i.e., the Korean Educational Longitudinal Study; KELS) with 6th-grade students (n = 7,065) from 446 schools was used to run a series of 2-level hierarchical linear models (HLM). 
KELS
An existing database (i.e., the Korean Educational Longitudinal Study; KELS) with 6th-grade students (n = 7,065) from 446 schools was used to run a series of 2-level hierarchical linear models (HLM). 
HLM