Early childhood education gains become basically undetectable within a few years after children start elementary school. This has actually been known for a number of years, despite politicians touting early childhood education programs like Head Start and various pre-K programs, but I thought I'd bring it up now because it appears that Vox got the memo.
But, despite the lack of any learning advantage, kids in programs like Head Start do better later on in life. The answer seems simple, and something I've been saying for a long time. It's all just really expensive subsidized daycare. Of course, providing safe and healthy environments during a critical age is good for children, particularly poor and at risk children which Head Start focuses on. Not to mention, having the option of subsidized daycare is a boon to parents who can focus their daily attention on work and not have to give up a good chunk of their paycheck.
So what's the takeaway from all this? Basically, that we should kill early childhood education programs that don't do much and replace them with less learning intensive preschool and quality daycare. It'd be both cheaper and could help more families at the same time.
I would also suggest focusing more educational attention on shoring up middle and high school children. That's where they actually fall behind and get lost. Elementary schools are actually just fine. The reason why politicians like to focus on early-childhood education despite it being pretty worthless is because it's easier to start and expand programs than to make changes in the school system that already exists.