I had one of these grannies as a student in my 5th grade elementary class my first year in Korea. A TV station came to film her for a story but they didn't do it in my class, otherwise I woulda been Waygook Famous! Though probably the gist of the news story would have been "godless foreigner drifter corrupts elderly treasure of the Han." Maybe it's for the best.

When I spent my last years working in Korea, I taught at a local elementary school where there was an entire class made
up of grannies except for 1 kid. In 2014 they were in the 2nd grade level, in the following year I taught them EFL but by their 4th grade level they could not do English except for that one kid in grade 4. They are now finishing their first year of the intermediate level.

Some people may wonder, why is it that these grandmas at the age of 70+ years are in grade school aside from just retirement?
Was it because of war that stopped them? Was it because of the fact that they are from rural areas that they were the last generation of girls in Korea who were denied education, based on traditions of the old Joseon Dynasty? Was it just socio-economic reasons?

It's not that girls were denied education, it's that families couldn't afford education, so boys were given priority.

Generally, worldwide boys are given priority when it comes to education. So, if you're living in a largely agrarian society raising 7 kids living in a hut 7 hours away from the capital city, you make sure all your sons are educated before your daughters. Since it's usually the boys that are expected to be the primary  source of income. Often only elementary is completely free (up to grade 6-ish), so most kids boys, or girls, will get education up to that point where you have to start paying to go to school.

In Korea's case up to the 80's elementary was free. So, most kids got that grade 1 to 6, education. And classes were huge and often multiple grades in one class. So, it's pretty easy to fall through the cracks when the teacher is trying to teach like 100 kids at different grade levels. Once you enter middle school, or higher, you had to start paying tuition. So, most poor families made damn sure that their sons got as much education as they can afford. If there was not much money left over, well your daughter(s) was out of luck then.

So, imagine going back a few more decades back to the 50's/60's where poverty was way more widespread, and like 80% of the population lived in rural areas, where the average birthrate was like 6.5, and getting to school required like a couple of hours walk. And a 4 year war, the chaos, and the societal recovery can derail your education. Also, a lot of poor families would try to marry their girls off as soon as possible (one less mouth to feed), once she hits puberty they'd be looking for suitors.