With the exception of a student I knew in grad school (who unimaginatively fabricated a lab report so there was zero individual variability within each of two comparison groups), anyone remotely versed in statistics knows that there’s always variability around an average; and typically there are plenty of uncontrollable factors (i.e., individual differences) contributing to that variability.
So that’s why, as a parent, I bristle when I hear about mamas whose pediatricians, friends, or family have inspired panic and worry over their kid not walking, talking, or eating exactly on schedule with milestone charts. The same goes for arbitrary cutoff dates, such as kindergarten enrollment. Obviously there is utility and convenience to standards, but variability is not equivalent to failure; and clearly many parents think in terms of the latter.
Elizabeth Weil addresses just these sorts of issues in her New York Times feature, When Should a Kid Start Kindergarten? She discusses the advantages and disadvantages of “redshirting” (cases in which parents intentionally delay kindergarten by a year so their kids have a physical and mental maturity advantage), how US standardized testing has prompted states to move enrollment dates so kids are older and can perform better on state tests, research on age and school performance (including cross cultural comparison), and the social and political history of school curriculum development and testing.
As someone whose favorite kindergarten activity was apple printing, it seems ridiculous to think of terms such as "high pressure"and "rigorous" in relation to kindergarten. Enough with the extreme parenting; let’s just let our kids be kids.