I know, I know - but even the late 70 = 30+ years ago.
Either system is fine by me - I don't really care. But the mixture of the do is disastrous. I'm used to it, so again it does not bother me much- I constantly switch from 2 languages, 2 cultures, 2 driving systems, 2 measuring systems, monetary systems - that's is fine by me (it's actually very good for ze little grey cells,as Poirot would say). You must agree that selling the example of selling carpet in £ per su yard, then sold in metre widths by the linear foot was farcical and confusing, no!? But we do live in a 'global' economy, and failure to adapt is costly.
Also how can we help our grand-children with homework, etc, if we do not understand what they are supposed to learn?