Abstract The outputs of secondary education are the main inputs of university education. Therefore, high-quality inputs into university education can be assumed to yield excellent outputs, which is a major goal of any higher-education institution. The present study compared the outputs of secondary education, as measured by students' grades, to those same students' grades from the first year of university. Grades for the first academic year of university are considered the most important in that they significantly affect students' subsequent academic careers by setting the tone for their pursuit of excellence [12]. To measure the relationship between student's grades at the secondary-school level and at the university level, the present study used the Pearson's correlation coefficient (r) and the Expectation Maximization (EM) algorithm to cluster students into two groups. Then study measured the characteristics of each group using the open-source software programs WEKA and SPSS. The study used the academic records of King Khalid University (KKU) students, specifically those students in the Faculty of Administrative and Financial Sciences (FAFS). Although it is widely believed that high grades in secondary school predict high grades during the first year of university study, the present study found that there was a very weak correlation between grades during these two periods. The results showed that secondary-school grades do not predict grades during the first year of university. However, the results showed that the average rate indicates some variations in the characteristics of the two groups during the first year of university study. Finally, the study identified a number of recommendations for improving the quality of higher education inputs.   Keywords: Academic performance, Secondary output, Higher education output, Data mining