The purpose of the study is to reveal the effects of PLCs(Professional Learning Communities) within schools in Gyeonggi Province. To this end, using data from the 6th wave of the Gyeonggi Educational Panel Study(GEPS) data, we analyzed how PLCs influences students academic achievement. The results of the study are as follows. First, the more time teachers cooperated and PLCs actually were helped teachers, the PLCs increased teachers morale and engagement. Second, students were aware of the same positive changes as teachers who experienced PLCs. Third, increased teachers morale and engagement affects students academic achievement through affective changes of students and changes in teacher-student relationships. It is noteworthy that both collaboration time and qualitative satisfaction bring positive changes to students, but in particular, the qualitative aspect of PLCs operation had a greater impact on students academic achievement than the quantitative aspect of PLCs. In conclusion, we confirmed the effectiveness of the PLC within schools and discussed how to support to the PLCs policy that PLCs should operate practically with this study.