Guidance Given on Young and Disruptive

New study finds support for pre-K teachers is key in reducing number of expelled prekindergartners.

The headlines seemed shocking. Young children—not even old enough for kindergarten—were being expelled from state-financed education programs at higher rates than for older students in K-12 schools.

Now, the same Yale University researcher who drew attention with those findings in 2005 is recommending steps pre-K programs and policymakers can take to reduce the expulsion of preschoolers with chronic and disruptive behavior problems.

Prekindergarten programs should refrain from removing children whose behavior is troublesome, and instead should work to find solutions, Walter S. Gilliam recommends in a study released this week . Reducing preschool class sizes, giving teachers access to expert advice from mental-health consultants, and making sure teachers—especially those working in full-day programs—take regular breaks throughout the day are also ways that early-childhood programs can avoid expelling youngsters who are “most in need of classroom socializing opportunities,” writes Mr. Gilliam, the director of Yale’s Edward Zigler Center for Child...