Overall, Northern's fall 2007 traditionally admitted entering freshman class had an average high school class rank (percentile) of 66 and an average ACT score of 23. NIU's graduation rates are similar to the average graduation rates of other NCAA 1-A institutions. This compares favorably with the national average ACT score of 21 for college-bound students. The following chart demonstrates the relationship of high school rank and ACT scores and NIU's graduation rates for the fall 2001 cohort. The table includes all students admitted through traditional admission who have ACT/rank information.
| ACT Score | 2nd Quartile | 3rd Quartile | 4th Quartile | Total |
| 19-20 |
- |
44 % |
63% |
49% |
| 21-22 |
- |
52% |
66% |
56% |
| 23-24 |
40% |
51% |
71% |
57% |
| 25-26 |
34% |
55% |
75% |
60% |
| 27+ |
38% |
55% |
77% |
66% |
| Total |
41% |
53% |
70% |
56% |
Source: NIU Institutional Research
"...Students with above-average academic abilities and preparation have higher graduation rates."
- Robert Burk, Director,
NIU Office of Admissions