[Luc]

The grandparent means 'passing grade', not 'pass rate'.

[rmc → Luc]

Yes. Perhaps a dialect difference. We'd say "pass rate" to mean "get less than this and you fail, more and you pass". We don't tend to use the word "grade" here for results in tests, to my ears it sounds very Amercian. ☺ We'd say "mark".

[dpritchett → Luc]

Thanks! I couldn't quite wrap my mind around a school with 60% per-period attrition.