Your article Re “Too Young for Kindergarten? Tide Turning Against 4-Year-Olds” (front page, May 28) doesn’t mention another implication in increasing the legal age of kindergarten entry: a decrease in the diagnosis of attention deficit hyperactivity disorder and the use of Ritalin-type drugs.

Several studies have shown higher rates of diagnosed A.D.H.D. in children who are not 5 by September of their year of entry to kindergarten. At fifth and eighth grade, these children are nearly twice as likely to be using a drug like Ritalin or Adderall compared with their older peers.

Many children, younger just by several months, are simply not ready developmentally to handle the increased academic demands of the last 20 years on kindergartners. This academic stress translates to increased agitation, inattention and hyperactivity, especially in boys.

California’s enlightened decision to add a state-supported pre-K transition year for 5-year-old children born after September should over time decrease the number of children taking psychiatric drugs.