The purposes of this research were: 1) to study students’ learning achievement in mathematics problem solving skills using the search, translate, answer, and review (STAR) strategy and compare it to the 70 percent criterion, 2) to compare students’ learning achievement before and after instruction using the STAR strategy, 3) to study the problem solving skills of students using the STAR strategy before and after instruction. The population of this study were 410 Prathomsuksa 5 and 6 students at Lueangchan Coordination Center under the Office of Chanthaburi Education Service Area 2 in the second semester of academic year 2016. The sample in this study was a group of 15 Prathomsuksa 5 students and 21 Prathomsuksa 6 students. The sample was selected by purposive sampling since the population had mixed knowledge and abilities. The research instruments used were: the STAR strategy learning activities lesson plan, learning achievement test and pretest and posttest of mathematics problem solving skills. The statistics used for analyzing the collected data were: mean, standard deviation and t-test.
The results of the research were as follows: 1) the learning achievement of students using the STAR strategy was higher than the criteria of 70 at the statistically significant level of .05, 2) the students’ learning achievement, as measured by pretest and posttest, was higher in all aspects at the statistically significant level of .05, 3) the students’ problem solving skills, as measured by pretest and posttest, was higher in all aspects at the statistically significant level of .05.