The purposes of this research were; (1) to study computer-assisted instruction of foreign language subject group (English) on the principle of English grammar for Prathomsuksa 3 students to meet the efficient standard criteria of 75/75, (2) to study effectiveness index of computer-assisted instruction, (3) to compare learning achievement between the pre and post learning of students who learned with computer-assisted instruction and (4) to study students satisfaction on learning with computer-assisted instruction. Samples were 49 students from Prathomsuksa 3/10 of Anuban Nakhon Ratchasima School under Nakhon Ratchasima Primary Educational Service Area Office 1 in the first semester of 2015 academic year, obtained by cluster random sampling. Research tools were: 9 topics of computer-assisted instruction of foreign language subject group (English) on the principle of English grammar for Prathomsuksa 3 students, 18 lesson plans, 30 items of learning achievement test and 20 items of questionnaire on learning satisfaction. Testing duration was 18 hours and One Group Pretest-Posttest Design was used as research design. Statistical methods used in this study were mean, percentage and t-test for dependent samples.
The study revealed that:
1. The computer-assisted instruction of foreign language subject group (English) on the principle of English grammar for Prathomsuksa 3 students had its efficiency of 80.04/78.71 that higher than the specified criteria of 75/75.
2. The effectiveness index of computer-assisted instruction of foreign language subject group (English) on the principle of English grammar for Prathomsuksa 3 students was 0.5015 i.e. students knowledge was increased at 50.15%.
3. The learning achievement of Prathomsuksa 3 students in foreign language subject group (English) on the principle of English grammar at the post learning was higher than the pre with statistically significant differences of .05 levels.
4. The students who learned with computer-assisted instruction had their satisfactions overall in high level (X-bar = 4.29).