The objective of this research was; to study best practice in small school management under the Office of the Basic Education Commission, to explore the small school development model, and to study the results of the using the small school development model by using professional learning community in mathematics and sciences subjects. The research was divided into 3 phases: Step 1: Study the best practices in small school management. The sample were a small school with O-NET test higher than the national average ONET test in academic year 2018. Step 2: Finding the small school development model by focus group were organized between education administrators, school administrators and teachers. And Step 3: Study on the effects of small school development model by using professional learning community. The samples were 3 small schools which O-NET test in mathematics and sciences subjects below the national average O-NET test. The data were analyzed by mean, standard deviation, t-test, and content analysis. The results of the research showed that 1) best practice in small school management consisted of learning management that allows teachers to be fully self-developed and students enjoyed learning, 2) small school development models consisted of goal, planning, action, observation, reflection, and strengthening, and 3) the results of using the small school development model by using professional learning community were found that the students had achievement in mathematics and sciences subjects statistically higher than 70% at the .05 level. They had attitude towards mathematics and sciences, and teamwork in high level. From the follow-up, it was found that in the academic year 2019, two out of the three schools in the sample school had higher O-NET test scores than the national average.

Best Practices, Small School, Academic Achievements, Attitude Towards Mathematics and Sciences, Teamwork