In 19 education systems, teachers in private schools collaborate more frequently by exchanging ideas or material than teachers in public schools do, while only in the Netherlands do public school teachers collaborate more than private school teachers. When school principals reported that teachers co-operate by exchanging ideas or material, the average 15-year-old student in OECD countries scores 9 points higher in science; in Slovenia, the average student scores 36 points higher. According to the report, Supporting Teacher Professionalism (OECD 2016c), a collaborative culture also shows one of the strongest associations with teachers' self-efficacy and job satisfaction.