Most of, if not all, the administrations of universities will describe their academic performance as "great" & their students as "fantastic" but it is hard for scientific persons to "buy these goods". The academic performance & success of university students can be measured by "external" neutral sources. A typical university functions as teaching-research site with various percentages of the 2 activities & with eventual output of graduates in the production line. The qualities of these "human products" can be detected in the workplaces to which they have moved. Very simple easily-phrased "clever" questionnaires can be directed to the employers & few staff mates will throw the light upon the students to reflect the status of the university from which they have come. Also, the standing of the graduate students in interviews, pre-work tests, and postgraduate studies can also be part of its evaluation. In my opinion, it is one of the duties of the ministry of education to form independent committees to assess the universities regularly by following up the suggested measurements.
Based on empirical evidences, academic performance of students can be measured using their results. One of the reliable scales for questionnaire rating is Likert rating scale which has: Strongly Agree (SA) Agree (A) Strongly Disagree (SD) Disagree (D).
You can look at articles that discussed on academic performance for better understanding.
Your imoportant question (Can anyone suggest a good scale for measuring the academic performance and success of university students?) has unfortunately received 4 replies so far. My suggestion is for you to send it by the message system in Research Gate to those who follow you or you follow them. I am looking for a more active discussion of this topic.
As academic success is not limited to GPA, a number of other measures have been incorporated in the sccuess equation, for e.g. "student engagement". See the NSSE - national survey on student engagement
actually I am looking for the best measurement of academic performance among students with learning disabilities (LD) , I could not found the measurement .