There's a name for this phenomenon: the "Matthew Effect," from Matthew XXIV:29: "For unto every one that hath shall be given, and he shall have abundance: but from him that hath not shall be taken away even that which he hath." Basically, children who acquire facility with language at an early age continue to build on that advantage throughout their lives. Children who lack that advantage correspondingly suffer more and more from it. The difference can be graphed. Imagine what the upper curve would look like if it began its upward climb at age two! (Thanks to BalancedReading.com.)
The SAT statistics distressed Ana, who has always realized the importance of language proficiency in young children. She made sure that her babies were exposed to many languages (in Distant Cousin: Repatriation), and that they were helped to learn to read (in two languages) in their preschool years (in Distant Cousin: Reincarnation). Her goal was not to produce geniuses, but rather children who found learning exciting and easily accessible. The techniques are simple and have been discussed elsewhere in Ana's blog. (See below.)
To be sure, it is also worrisome that education budgets are shrinking, teachers are being let go, and class sizes are increasing. Having a citizenry which is willing to allow this to happen is another problem, however. In the meantime, there is much that parents of young children can do on their own.
More on early education: