What is "sub-Varsity"

Several GC posters have stated more than once that the LPD is the only district that allows 9th graders on there JV football teams.

to me it looks like it will kill any 7th/8th grade teams unless the team chooses to ignore the rule in which case it has no real teeth since as far as I can find the only penalty would be forfeiting the JV/Sub-Varsity Game that the ineligible player played in