You have to be honest though. If they don't want regrets if they are interested in a specific field of work like healthcare for example then straight up I would tell them, you need to work hard now if you want college to be easy (or at the very least manageable) lol. I didnt care that much for studying myself but I had enough self discipline and smarts to get high grades without needing to study much and 95% of the time in middle school and high school I had no actual homework unless it was a project or essay. My mentality was that if I'm going to school no matter what, might as well make it so that the benefit outweighs how much work I'm putting into it ╮(￣▽￣)╭. Why wait till 18 to learn discipline/self study if on top of it all you're on the low end of the academic percentile.
However, if the person really would never be ending up interested in a field pf work that needs minimum higher scores, then yeah Cs get degrees
to my siblings when they didn’t care about was at least do the bare minimum. C or 70% is passing- aim for that if you don’t care or have a hard time