Several decades ago, it used to be that the majority of students coming from South Korea to this country as foreign students was college grads seeking grad degrees. Then, gradually over the past decade, we started seeing a large flux of high school students seeking to earn college degrees. Now, there are many kids coming to this country for even K through pre-high school education. These families are typically well off. Dads of these families stay behind in South Korea to keep producing the necessary income while moms come along with their children to manage their education. Such dads are known in South Korea as Gireogi appa (기러기 아빠). It’s estimated that there are approximately 200,000 such families in South Korea today: https://en.wikipedia.org/wiki/Gireogi_appa
For these Gireogi families, it’s worth the family separation, money and sacrifice to avoid the college preparation hell. For those without the financial means, they resort to hooking up their kids with relatives in this country, even friends. We were once asked to host a child of our family’s friend. Although a close family friend, we had to politely decline for various personal reasons.
When I was preparing my sons’ colleges, a lot of work went into it for years. I never once complained, though, because I always had the images of those in South Korea going through hell and mine’s been a nice leisurely walk in the park in comparison.