Cal Poly Pomona accepts about 60% of all applicants, so it is a bit more selective than many of the schools in the California State University System. In the graph above, the green and blue dots represent accepted students. The majority of students who got in had GPAs of 3.0 or higher, SAT scores (CR+M+W) of 1450 or higher, and ACT scores of 20 or higher. However, note that there are some red dots (rejected students) hidden behind the blue and green. Some students with grades and test scores on target for CSUF still get rejected.
Unlike the more selective University of California System, the California State University admission process is not holistic. In other words, admissions are based almost entirely upon grades, test scores, and your level of college preparedness. With a few exceptions, Cal State applicants do not need to submit letters of recommendation or an application essay, and extracurricular involvement is not part of the standard application. Thus, the reason why an applicant with adequate scores and grades would be rejected tends to come down to a couple factors such as insufficient college preparatory classes or an incomplete application.
To learn more about Cal Poly Pomona and some of the admissions factors, check out these articles: