“…The five factors related to school and classroom environment, together with leadership quality of school principals, seem to have a significant role in students' achievement in mathematics in TIMSS 2015, and possibly other years too. While considering school planning and educational polies, other factors such as mathematics teachers' perceptions of TIMSS [39], and interdisciplinary approaches to collaboration, communication, and creative educational practices could be enhanced, with greater prospects, decentralized priorities, and STEM/STEAM movement as a process [67] to improve students' achievement in mathematics and science in TIMSS, PISA, and PIRLS. Therefore, these five school factors should be studied in conjunction with other factors related to teachers, students, parents, and interdisciplinary activities.…”