The present study is an attempt to find out the difference in intelligence and academic achievement of secondary school students. The present study is conducted on a sample of 160 secondary school students of government and private schools of Rohtak district of Haryana. General Intelligence Test by Dr. S.M. Mohsin and Academic achievement scores are taken on the basis of marks obtained in 9th class. Mean, Standard Deviation,‘t’ test and Karl Pearson’s Product Moment Coefficient Correlations tests are used to analyse the data. The findings of the study reveals : (i) Private school students are found more intelligent as compared to government school students; (ii) students having high intelligent were found to have better academic achievement than those students with low intelligence; and (iii) a significant and positive relationship is found between intelligence and academic achievement of secondary school students.