In the name of boosting academic performance and giving struggling kids a better shot at succeeding in first grade, California appears to be headed down the slippery slope to universal preschool, never mind that state voters rejected such a plan when Rob Reiner got it onto the ballot in 2006.

This time they won’t have that opportunity, because the legislature has already passed the bill and sent it to Governor Schwarzenegger’s desk. He’d be wise to veto it.

Note, though, that what’s on offer this time isn’t called preschool. It’s called “transitional kindergarten,” and it’s not yet universal. For the moment, eligible participants will be children whose fifth birthdays fall during the months of September, October, and November. Under longstanding California practice, they may enter regular kindergarten when they are still 4, so long as they turn 5 by December 2. (In most states, the cut-off date is earlier in the autumn.) But a variety of educators and politicians have declared that kids this age aren’t ready for the academic demands of modern kindergarten, so they should first have a year of preschool.

If press accounts are to be believed, the usually sensible California Legislative Analyst’s Office declared this measure cost-neutral because the savings from having fewer kids in regular kindergarten will supposedly pay for the transitional program. That makes no sense, however, as taxpayers will end up paying for these youngsters to attend two years of school rather than one before first grade — a curious lapse of fiscal insight in a state with America’s worst budget problems. In effect, the legislation creates a new entitlement — another year of public school — for one-third of all young Californians.

Nor will it stop there. One can already hear the clamor from parents of boys and girls born on December 3 and December 17: Why are you discriminating against our children? And what about those with birthdays in January, March, even May? Why not just offer “transitional kindergarten” to every four-year-old in the state?

That’s more or less what Florida, Georgia, and Oklahoma have done, though they call it preschool and don’t entrust it solely to public-school systems. California’s notoriously powerful teachers’ union, however, can be counted upon to demand — and its friends in Sacramento to ensure — that the new program will be the exclusive property of the public schools. That means, of course, that as it grows into a universal entitlement, the public program will eviscerate any number of extant private preschool operators. Why should parents, even prosperous parents, pay for such services when the state is giving them away?

Is this all part of a grand conspiracy to enlarge the public-education monopoly and employ more teachers? Don’t dismiss that thought. Don’t suppose that school systems that do a miserable job of educating 5- and 7- and 17-year-olds will do miraculously better with 4-year-olds. And don’t forget reams of research showing that few preschool programs, even good ones, have lasting effects on kids’ academic achievement.

To be sure, plenty of 4-year-olds are ill-prepared for kindergarten. (Plenty of 15-year-olds aren’t ready for high school!) Others are quite ready, however, and this statutory change will place another hurdle before them and their parents, needlessly confining them in pre-K for a year during which they could be accelerating.

Public policy is simply too clumsy to distinguish youngsters who need publicly financed preschool (especially since those who need it most will need it long before age four) from those who are ready for kindergarten (or even first grade) and those whose parents have made satisfactory preschool arrangements on their own. One size does not fit all. Critics of the legislation begged for more flexibility, more opportunity to tailor the age of entering kindergarten to the circumstances of the individual child. A shred of that can still be found in the measure that was enacted, but the chance to start before one’s fifth birthday will be called “early admission,” and the school system gets to decide who is admitted.

Ugh.

Schwarzenegger should reject this bill as a bad move for taxpayers and children alike.

This commentary is also posted at the National Review Online’s “The Corner” blog.