Teacher professional development, in particular, has been at the center of efforts designed to increase teaching practice and the learning of students. The aim of the study was to investigate the effect of the ?teacher-led PD for teachers? program, developed by the researchers, on students? achievements. The study was conducted with six high school physics teachers and 306 students in Turkey. The professional development intervention lasted for seven weeks, and teachers had 21?hours of professional development regarding modern physics at high school level. The results of ANCOVA showed that there was a significant effect of the teacher-led PD for teachers program on students? achievements. The successful implementation indicated that the teacher-led PD for teachers program possesses effective characteristics of professional development and can improve student achievement.