Flag-man...
I have never heard of that rule. Even when I was at Riverside during our top years, we did not have a middle school or level below JV team. We had Freshman and Sophomores on the JV team. Drew Stephen was one of the first 8th graders to play JV.

That could not be a blanket SCHSL rule b/c then smaller schools like Hanahan (where I was for a year) would never be able to field a JV team b/c many of those schools rely on a mix of 7th-sophomores to field a JV team. It could be a school-by-school rule at schools where their feeder schools may have a middle school team or there is enough talent and interest to field a B-team. I do not know of many true middle school soccer teams as opposed to many schools that have middle school (or B-team) football and basketball teams.

I know that Brookland-Cayce has a level below JV (I think they call it a B-team) so maybe Kevin or Kyle could speak a bit clearer on this issue. I think that anyone 8th grade or up should be eligible to play varsity. If you have enough skill to make a varsity team, you have enough skill not to get seriously hurt.