The entry characteristics of students from Junior High (early high grade) level into Senior high schools (SHS) can have many repercussions on their academic performance. Such entering characteristics such as age, weight, height, gender, formal school status (grade level of school), background status (whether day, boarding or hostel) and Entry Grade of Students can have advert effect on their academic performance. By adopting a quantitative approach to under study 166 sample students placed into Ghanaian SHS by the computerized school selection and placement system (CSSPS) in Ghana, the study variables were all tested to be significant under z-test, correlation assumptions and regression parameters. We noticed a significance effect of students entering grades and age in the model parameter estimation as moderately correlated with performance in Secondary school. Our analyses of the contrast effects of students’ background as an entry characteristic reveal that, students from Villages, and cities/urban with students from towns was highly significant. We conclude that, on the average, students from towns and nearby villages are performing better in Atiwa Senior High Schools as compared to those from cities. It is recommended to stakeholders of education to consider such entry characteristics of students and place them at their most preferred schools beyond imposition. Researchers can further investigate into other variations existing among such study variables with respect to their dynamic effect on students’ academic achievement.