Traditional web-engine searches have many virtues, but there are limitations to these these tactics when searching Archives.
Materials are frequently overlooked if search terms do not include historical terminology. Searching for "Grade Point Average" returns a handful of matches in the archives database. However, searching for "scholarship report" returns more results.
Privacy laws may restrict access to some materials, including individual grade point averages. To identify unrestricted files that will give compiled statistics for a fraternity, sorority, or dorm, it helps to consider "who compiled the grade reports and why?"
The search for statistical data is only as successful as the searcher is well-informed. If you know who produced the reports, you will know where to look. If the report was produced for the Dean of Students then you know to go through those files. The Dean of Students academic reports are largely unrestricted because they omit grades for individuals and focus on composites for organizations. For example, grades for all fraternity members are reported to the dean but not individual students. Oftentimes, individual fraternities and sororities include individual student grades--restricted by law--with their yearly reports. If this is the case, Dean's files sometimes include summaries on Greek house academic performance and are therefore unrestricted.
Keep an open mind and search broadly. A variety of search terms may return relevant information, such as files labelled "House Averages" or simply "Grades".
As the image above indicates, the Daily Illini is another information source. For many years the paper published grade point averages for fraternities. Use their search interface and enter the phrase "grade point average".
Certain issues will affect your ability to find the material and use it once it is identified.
Charts that compare grade point averages for all fraternities on campus were created by national Greek organizations, including the Interfraternity Council Member Fraternity Files. However, finding these charts may prove problematic, as they reside under a variety of terms. The chart below, and several others, were simply filed under "Fraternities" and found in 41/2/5.
In short, the more thoroughly you explore a topic, the more likely you will find information.