They have different rules to be eligible from JUCO depending on how you end up there.Justin Martin only did one season...Leonard Little back in the day, sure there are many other examples. I know Kamara's was his second academic year.
If you fail to qualify out of HS I think you have to get enough credits at the JC to get an associates
IIRC Martin left high school early when it became clear he wasn't gonna qualify and got his GED and so because he didn't technically fail to qualify out of HS(because he didn't graduate) he could do just one year.
I could be completely wrong but I think that's how it works