OTOH, I think what indigo and CD mentioned about inquiry would probably be more to the point, as "maturity" is so often a code word for "we're reluctant to do this, either because there is institutional bias against early entry, or because we're afraid we won't know what to do with her". When we entered our first early into 1st grade (skipped K), it took ongoing discussion and assessment from April until the end of August to attain consensus. And this was with a school with which I personally had a long history of warm and professional relationship. In our case, staff were genuinely concerned that this might be to the detriment of our child; we had to work through their fears and concerns, as much as demonstrate academic appropriateness.
Yes. This is also true in negotiating on-time entrance for 2Es and children with disabilities, who often present as "immature" even if they are thoroughly ready to take advantage of kindergarten-level academic learning.
IMO "immaturity" should rarely or never be a reason to hold a child out a year; instead, a plan should be made to teach the executive function skills that will help the child succeed.
