Stephen Krashen is a professor emeritus at the University of Southern California, where he taught linguistics.

He comments here in response to an earlier post about the Common Core standards:

What this excessive detail also does is
(1) dictate the order of presentation of aspects of literacy
(2) encourage a direct teaching, skill-building approach to teaching.
Both of these consequences run counter to a massive amount of research and experience.

There is very good evidence from both first and second language acquisition that aspects of language and literacy are naturally acquired in a specific order that cannot be altered by instruction (C. Chomsky, 1969, The Acquisition of Syntax in Children from 5 to 10. Cambridge: MIT Press; Krashen, S. 1981, Second Language Acquisition and Second Language Learning, Pergamon Press, available at

There is also very good evidence that we acquire language and literacy best not through direct instruction but via “comprehensible input” – for literacy, this means reading, especially reading that the reader finds truly interesting, or “compelling.” (Krashen, S. 2010.The Goodman/Smith Hypothesis, the Input Hypothesis, the Comprehension Hypothesis, and the (Even Stronger) Case for Free Voluntary Reading. In: Defying Convention, Inventing the Future in Literacy Research and Practice: Essays in Tribute to Ken and Yetta Goodman. P. Anders (Ed.) New York: Routledge. 2010. pp. 46-60. Available at