Due to a high level of competition in the 12th grade for university entrance examination, leading to popularity in taking extra classes among high school students. This is limited to poor people who cannot afford the course fees and may affect their O-NET scores. Our objective tried to answer that whether education inequality existing between the rich and the poor or not. We use O-NET score of 3 subjects (Mathematics, Science, and English) in 2013 and average household income of each province to locate the inequality of the test score between the rich and the poor. We selected the concentration curve to measure the inequality and the educational results were grouped into the quintile according to the household income in each province. The concentration index is computed and the results reveal that there is no strong inequality between the rich and the poor much following the test year. The results of concentration index are 0.0136, 0.007, and 0.0208 for the 6th grade, the 9th grade, and the 12th grade respectively. The index valued in positive area implied that the advantage group (Rich People) are having poor scores and other results are discussed.
Keywords: Education Inequality, O-NET Results, Concentration Index