Class-size reduction, particularly in early grades, is one of the effective strategies to improve education and academic performance. Not only students but also teachers can get the benefits of smaller classes. Students in smaller classes may receive better grades and exhibit improved attendance. For teachers, their teachings tend to be improved better because smaller classes allow teachers the space to create and develop new teaching strategies to improve student achievement. Success in improving academic performance can be seen obviously in some countries that use the strategy of class-size reduction such as the U.S. The U.S. Students in smaller classes has significantly lower drop-out rates and higher grades. For Thailand, there is no use of the strategy of smaller classes in academic institutions. Therefore, the students in Thailand have not been improved their learning potential as good as it should. The quality of educational standard of Thailand is quite lower when comparing with other countries using the smaller-class strategy. The article can present the benefits from small classes to readers quite clearly but there is some points that have not been fully considered such as how many students should be in the small classes to achieve the maximum benefits to improve their educational performances. Moreover, how long students have to be in smaller classes should have been discussed in the article as well.