Around 78% of browsers hitting the site are running IE8, and these will be parents making use of the portal to do stuff like check calendar dates, book appointments to see teachers, and check student grades.
We tried extremely hard to move the community onwards, including outreach to upgrade computers for families and so on. But in the end, they just don't want to move on from Windows XP because everything else is too confusing. Even if you make it look the same.
As for how often they're using the site... It's somewhere around 1/3rd of the parents hit it at least once a day using an outdated browser.
... Whilst their kids are using school-provided Thinkpads all running on Windows 10, or recent-ish school-provided iPads. (The school does all the maintenance on them as well).