Hart & Risley Turned Inside-Out

In Clayton Christensen's book, "Disrupting Class: How Disruptive Innovation Will Transform Education." I have finally come to the dreaded chapter on early childhood. In chapter six Christensen says flat out that America shouldn't invest in voluntary preschool because it won't work. He then uses one of the most important studies of early language learning, Hart and Risley's "Meaningful Differences in the Everyday Experiences of Young American Children", to argue that pre-k is too little too late to help kids' language development. The only supportive evidence he sites is this study. I doubt Hart and Risley would agree that preschool should not be funded because kids make the most gains in language development from 0-3 years old.
Christensen states:

"Rather than funding programs that hire people to substitute for parents who aren't succeeding at preschool talk, quite possibly we might have a greater impact if we taught children how to b e parents before they become parents."

I actually agree with the above statement that some prevention, especially parenting courses at the middle school level in health classes, would help prevent some language delays in all children. But, the reality is that Hart and Risley's study, published in 1995, did not account for the current economic environment. It was also completed before welfare reforms which required poor parents to work. At the time, teaching poor parents how to talk to their children may have been the only intervention needed but now, that would not be enough. What Hart and Risley do not say, and what Chirstensen takes for granted is that it is too late for a child who is 3 or 4 years old to gain language at a rapid pace.
This is why Head Start has, for approximately 15 years, included parent involvement and parent literacy training in its comprehensive services offered and required of parents. In fact, our program recently received an Early Reading First grant through VCU to implement, as part of a holistic literacy program, family literacy strategies based on Hart and Risley's work. To say that children learn most from 0-3 is not the same as saying kids don't learn from 3-5. Shouldn't poor kids have the chance to catch-up even if they do start out behind?