Baby Rocket,
Kindergarten screening instruments are "too basic" by design, as their usual purpose is to identify children in need of additional support. (North American public schools have government-mandated child-find requirements for identifying and offering remediation to at-risk students.) With regard to social readiness for kindergarten, the bottom line is whether they can make it through the school day (whether half or whole day) without feeling distressed--by the expectations for managing their behavior, sitting still, paying attention, following directions, etc.
And while height is on many protocols for grade acceleration/early entry, I view it as a relatively minor consideration (probably biased by my own, more efficient, length!). In any case, weighting height too heavily in grade placement would result in many entering high school students (especially boys) being held back for three years, as well as in systematic discrimination against other protected classes, since height is sometimes distributed somewhat differently by ethnicity/national origin.
