사교육이 · 사교육을
private education, private tutoring (outside school)
Example
많은 학생들이 방과 후에 학원에서 사교육을 받아요.
Many students get private tutoring at cram schools after school.
Word parts
사 private+교 teach+육 raise
Literally 'private education'.
Good to know
It means tutoring and cram schools outside regular school, not attending a private school.