As you'll know, the cognates are so widely spread that the teacher's proposition could hardly have been more ridiculous. But as kids, we weren't to know that.
It indeed is ridiculous, the Dutch took this dialect suppression even a tad further and invented terms for using loanwords or loan translations from fremmet languages. And this started pretty recently around the 19th century, at the end of this century only 10% of the Dutch population spoke standard Dutch, and the rest of the country spoke a "Low German Dialect". In this era, it was called literally translated as "Nederduitsch". To suppress the use of those dialects they invented the term "Germanism" which means words that are directly translated from the neighbouring country German into Dutch. This was considered Silly, Ugly and Improper use of the Dutch language, Post WWII this anti-German idea became even more of an issue.
The best example I have is the word English also known as the German invention and the word "Autobahn" which simply is the correct Germanic noun, we Dutch also know the words "Auto" and "Baan" as correct words. But "Autobaan" as a combination is considered Ugly Germanism and should not be used. The standard Dutch linguists invented a new word combination that says the same (Synonyms) but sounds different, still Germanic words that Germans also know and have but don't use in this fashion. Namely "Auto-baan" is ugly and incorrect Dutch and became "Auto - Snel - Weg" The Germans know "Schnel" and also know "Weg" so it's still Germanic language but they don't say "Auto schnel weg" and that was the goal. Suppress and discourage the German influences in the Dutch language to create a proper self-identity.
Meanwhile, the noun Dutch is derived from Deutsch and Deutsch is German. And speaking proper standard Dutch is still and stays a Germanic dialect.
There are books written about it and we have a crapload of words that are deemed ugly Germanism and even today there are still nationalistic language purists practising this idea and laughing at you when you use words that are deemed Germanism. A teacher still would give you a minus point for using words in this list. They do not realise how silly they actually are with inventing different word combinations that still are Germanic words to create different sounding words than the neighbours would use. Simply to establish their own identity, create hard borders and drive people apart, this is all it does.
Nowadays half a century into the process Germanism went a tad into the background since we also have a lot of Anglicism and Galicism in the Dutch language. Anglicism is loanwords from English such as Kicks, Shop and Cool etc. and Galicism is from French such as Toillet, Trottoir and baguette are adopted as proper standard Dutch.
A lot of dialects are about to go extinct with national language standardization and now groups are standing up and forming to preserve this heritage. And that's a good thing, knowing your dialect and also knowing the standard makes you bilingual and only can encourage people to become polyglots and be less fremd.
