Possibly the institution is using IELTS to compare its students to other tertiary institutions in Hong Kong. If the average band is around 6, then the institution is not doing as well as HKU for example, where the average is around 7.
Students who are entering university in Hong Kong on a degree programme has a DSE level 3. This is something like an IELTS band 5. Those who enter HKU humanities courses (such as Law) probably have DSE 5* or above, and they would be getting Band 7 or higher in IELTS.
While the highest band in IELTS is Band 9, many native speakers would not get that, with international school kids often getting Band 7 or 7.5 - often their range of vocabulary is not wide enough, and their writing skills are weak.