I grew up in Australia with metric, with parents and grandparents who grew up with imperial units. Though it seems things happened differently in Australia as my parents (and possibly grandparents too) converted to thinking in metric at least most of the time. That said, it's still reasonably common to hear people quoting their personal height in feet and inches. Even then, most people born post-metrification don't really have a grasp of imperial units (the exception tends to be people who have spent time in the US).