Not true in my experience. I have a DS in Catholic K now. There are 5 year olds than 6 year old red shirters. Back when FFX had half day K, lots of families would do Catholic K and then switch to public in 1st.

Doubtful. They all have about the same curriculum for language arts and math. If anything, catholic schools will have more children redshirted.

Has anyone sent their young 5 child to Catholic school for Kindergarten and then transferred to public school for a second year of Kindergarten? We have found that some public Kindergartens in Arlington are more at a 1st grade level and are considering sending our child to Catholic K first.