The ability to construct scientific explanations is a vital goal of learning science at all levels. Students from different backgrounds are likely to have this ability differently. This research aimed to assess Thai grade 10 students' ability to construct scientific explanations, examine differences based on learning achievement, attitude toward science, and school size, and find correlations among these variables. The study included 231 students from Phetchaburi province, Thailand, with 77.5% showing moderate ability levels. The research identified significant differences in students' ability levels based on their learning achievement, attitude toward science, and school size. The levels of students' ability correlated with their learning achievement, attitude toward science, and school size. In addition, students with high learning achievement, and positive attitudes, and who attended larger schools tended to have higher ability levels. However, there was no significant relationship between the levels of students' attitudes toward science and school size. These findings highlight the importance of considering individual differences and backgrounds when teaching science, particularly in terms of learning achievement, attitude toward science, and school size.