I was aware that the minimum voting age has been challenged in Canada. That's something I mentioned a while back. However, I only very recently learned of some similar developments in New Zealand.
I gather than their Supreme Court has already ruled that restricting the vote to adults (18+) amounts to age discrimination against 16- and 17-year olds. Nonetheless, according to this article on The Conversation, it seems that proposed legislation to lower the voting age for national elections is unlikely to proceed - although it seems that the age may be lowered for local elections only, partly because this change only requires the support of a simple majority, rather than a 75% super-majority, of MPs. That may also be of interest when I teach about majoritarianism and constitutional entrenchment.