You’re getting downvoted because this isn’t how US systems generally work in theory, but it’s a good point because this actually is how many of them work in practice. Schools are extremely loath to fail students because, well, parents flip.
So if you're just very academically limited and have a ceiling to what you can achieve what do you do? Repeat one school year for the rest of your life? After how many attempts do they let you out so you can earn some money?
In all states there is a process for exiting school by or before the age of 16. And you're right: Societal pressures and funding tied to student failure rates caused many schools to abandon the traditional method of holding back students who were not ready to proceed to the next year's studies.
> So if you're just very academically limited and have a ceiling to what you can achieve what do you do?
You can choose to keep applying yourself until you pass. Or, in the case of a student who doesn't apply themself or wish to continue with school they simply leave. Job opportunities will be limited to those which do not require an education, of course.
>After how many attempts do they let you out so you can earn some money?
You have to be in school until you're 16 (age varies depending on state), so the number of attempts is entirely dependent on your grade. If you fail at 10th grade you can drop out right there.
What is the plan if like this individual you just don't turn up or apply yourself? Are you never officially released from school? Are you truant for the rest of your life? Are you able to get a job or do you show up on background checks as being 'still at school'?