I believe Young-sam from Wengmak was lucky enough to get into a high-ranking school due to under-enrollment

Not just anyone can come in last.
To truly be the bottom of the class, you either have to blatantly avoid writing the answers,
or a slow student has to be placed in a group of truly bright students.
I cautiously predict that Young-sam and his tutoring gang might fall into the latter category.
I remember from my own middle school days, there were kids who
luckily got into upper-middle tier high schools because of under-enrollment.
Back in the 200-point era, schools where the cutoff was 140 or higher.
I suspect Young-sam and his group ended up in a place like that.
No matter how dim-witted someone is, if they receive that much academy tutoring,
even if they are distracted, they should be able to manage some memorization subjects.
In a high school that faces under-enrollment every year—where even students scoring below 100 get in—even if they are distracted and don't study, they shouldn't be able to rank dead last on an exam.