One of the big problems converting my DDs school marks to something understood in the US is that 90% at her school is rare. The best mark in a subject might be in the low 80's. Alternatively she topped a subject one year with 97% and still didn't get an A. The school marking system is unknowable and seemingly quite random. In one year she got a mark in the 50s for Physical Ed and Health despite nearly topping the Health component and having a medical exemption for the physical stuff. Horrible teacher. If you ask questions you get a shrug of the shoulders and a bad reputation!