The earlier children become familiar with the printed word, the better readers they become. And a study from Ohio State University found that preschool is a good time to start. Not reading, exactly, but letting children know that what is being read to them is contained on a printed page.

Preschool teachers who made occasional references to the printed page during storybook reading gave a boost to children's reading, spelling and comprehension that still lingered two years later.

At first, printed words are just squiggles to children. This is their first step at cracking the code and learning how to read.

It starts small: pointing out letters and words on the pages, showing capital letters and showing that you read from left to right and top to bottom. At first, printed words are just squiggles to children. This is their first step at cracking the code and learning how to read. And it only takes a small change for preschool teachers to start children on this road since storybook reading is already part of most preschool classes.

The study was part of project STAR (Sit Together and Read), a randomized trial testing the short and long-term effects of reading regularly to preschoolers in the classroom.

The study looked at more than 300 children in 85 classrooms who came from low-income homes, started with below-average language skills and were at substantial risk for later reading difficulties. The classes were split into three groups, with teachers in all classes reading the same 30 books to the children over a 30-week period.

Teachers in two of the groups were trained to make specific references to the books' print while reading to the children. One of these groups (high-dose) had four reading sessions per week, the other (low-dose) had two reading sessions per weeks. Teachers in the third group weren't prompted to make any print references; they were told to read to the children as they normally would. This group had four sessions per week.

When the children were tested one and two years later, those from the high-dose group scored significantly better at reading, spelling and word comprehension than did those from the group whose teachers weren't prompted to make print references. The benefits weren't as clear for children from the low-dose group, though they seemed to have slightly better skills than the children from the classes that didn't emphasize print referencing.

Previous studies by these and other researchers have shown that preschool teachers do commonly make occasional print references, they just don't do so very often. One study found that teachers on their own make about 8.5 print references per reading session, while those trained to do so made about 36 per session.

It's never too early to show children that you can't make a cookie without a cook.

An article on the study will appeared in the online edition of Child Development in advance of print.