1) School type 
Japanese privately run, after-hours tutoring school geared to help elementary and secondary students perform better in their regular daytime ... [1 related articles]
Privately established schools that teach either academic or nonacademic subjects. Academic juku offer tutorial, enrichment, remedial, and examination preparatory classes that supplement regular school work. Most hold classes after school and/or on weekends.
(in Japan) a school, attended in addition to one's normal school, where students prepare for college entrance examinations.