The purposes of this research were 1) to develop and evaluate the quality of an online computer assisted instruction in computational science subjects for grade 8 students, 2) to find the effectiveness of the online computer assisted instruction together with 5Es instructional model in computational science subjects for grade 8 students, 3) to compare the learning achievement of the students before and after learning with the online computer assisted instruction together with 5Es instructional model, and 4) to find the satisfaction of students on the online computer assisted instruction together with 5Es instructional model. The sample group used in this research was 31 students of grade 8 students of Tamaka Wittayakhom School by the purposive sampling technique. The instruments used in this research were the online computer assisted instruction, the assessment form of the content, the assessment form of the techniques and methodology, the learning achievement test, and the assessment form of student satisfaction. The data were statistically analyzed using mean, standard deviation, and t–test dependent.

The research findings showed that: 1) the online computer assisted instruction that developed was consisted of 6 main items including main page, the content of programming designed in Python language, Python language variable, control code and operator, pretest and posttest, and developer, the opinion of the content experts and the opinion of the technique and methodology experts on the online computer assisted instruction were at the highest level, 2) the effectiveness of the online computer assisted instruction together with 5Es instructional model was 94.84/91.08, 3) the students who studied with the online computer assisted instruction together with 5Es instructional model had post-test scores higher than pre-test scores at .05 significance level, and 4) the students' satisfaction with the online computer assisted instruction together with 5Es instructional model was at the highest level.