Michael Rosen explains the difference between a phonics test and a reading test (Letter from a curious parent, Education, 31 January). In a phonics test, children pronounce words presented to them in a list. In a reading test, children have to understand what they read.

Of great interest is the consistent finding that heavy phonics training only helps children do better on phonics tests. It has no impact on reading tests. Research also tells us that the best way to get better on reading tests is reading. The best predictor of reading achievement, in study after study, is the amount of recreational reading children have done.

The problem is not insufficient phonics teaching, as some claim. It is insufficient access to books. For many children of poverty, their only source of books is the library.

Research also tells us that better libraries are associated with better reading test scores. The implication is obvious: invest in libraries and librarians, not in phonics tests.

Professor Emeritus Stephen Krashen

University of Southern California