My middle child went to a public HS where ~1/4 to 1/3 were "skippies." The high school started with a pre-HS grade (normally like 8th) then 4yr 9-12. Those who skipped a year had skipped 7th grade at their JrH and went straight from completing 6th grade into the pre-HS year. Sports wise they placed 2nd in state soccer son's Jr year, it was obviously a young team. Also about 25% of kids made National Merit each year.
Different issue but research has shown kids do better when start learning early (doesnt have anything to do with skip year) so I don't understand the hold back for kindergarten.