Teaching pupils their numbers in French is usually fairly straightforward until you get to 70 upwards. Soixante-dix (70) literally means sixty-ten; quatre-vingts (80) means four twenties and quatre-vingt-dix (90) means four-twenty-ten. Pupils often find this hard to get their heads around. I spent a year working in Switzerland where their version of French has certain differences – some vocabulary, a few grammatical constructions and numbers. Instead of the versions above the Swiss use septante, octante and nonante which certainly makes life a lot easier for non native speakers.
If you’re interested in other differences between le francais et le francais suisse there are a few websites that are worth looking at. My favourite is www.topio.ch which is quite a fun website.