Yobiko (cram school) questions

Hi everyone, I'm curious about Japanese yobiko schools (preparatory schools for university entrance exam). Are they usually for weak students, or stronger students, or both? Are they common among the general student population in Japan? Or do the high price tags prohibit most from attending? Thanks in advance!

"Are they usually for weak students, or stronger students, or both?"

Both. But keep in mind that those who go to university must achieve a certain level of academic ability.

"Are they common among the general student population in Japan? Or do the high price tags prohibit most from attending?"

It is very rare that someone can pass a public (not private) university entrance exam without the help of yobiko. Also if you cannot finance to go to a yobiko, you are most likely unable to finance going to a university. But there are some people who are successful enough at school to be able to go to a high school on scholership, and then achieve enough of a level there to go to university on scholorship.

At the same time, a lot of high school students proceed to private universities by achieving enough grades at their high school. Because if your grades are good enough, it is quite common nowadays to be admitted uni entrance through recommendations of the high school principal.

Thanks for the answers! :)

"It is very rare that someone can pass a public (not private) university entrance exam without the help of yobiko."

Haha, I thought that's what high schools are for.. But there are good private universities as well, like Waseda right?