An interesting question. When is education completed, anyway? But a potential way to answer the question is to look at conversion rates. Some digging would probably bring up some data for one religion in particular but at the very least we could establish an upper bound of ~87k in South Korea for that religion, granting the wrong assumption of all current members being converts post-education https://www.mormonnewsroom.org/facts-and-statistics/country/... Still, I'd bet it's > 0.

Ben Casnocha wrote: "Rule of thumb: Be skeptical of things you learned before you could read. E.g., religion."

You can convince a non-zero number of people of pretty much anything.