The time of entry into kindergarten is a time of importance for children, as the combination of health status, developmental status, and social/emotional maturity are key determinants for subsequent school success.
A child's readiness for school requires age-appropriate physical, behavioral, communicative, visual-motor, adaptive, and conceptual skills.3
Accordingly, in designing our assessment of school readiness, we used a multidimensional battery of well-validated cognitive, language, visual-motor, functional, and behavioral assessments, supplemented with assessments of neuromotor disability (i.e. CP) and neurosensory disability to assign school-readiness levels. This model has not been routinely applied to recent US, Canadian, European, or Australian cohorts.
Regardless of preterm birth, a large percentage of the general US population is not ready for school. Data from three US national surveys have been reviewed by the Center for the Future of Children.22
These included the 1993 National Household Education Survey and the Kindergarten Teacher Survey on Student Readiness, both sponsored by the National Center for Education Statistics. In addition, the National Survey of Kindergarten Teachers was sampled by the Carnegie Foundation. The data from these three surveys were combined to determine the proportion of children in the general US population who were considered ready for school. These surveys demonstrated that as many as one-third of kindergarten children may not have been ready for school in the early 1990s.22
In a study by Reynolds, children who were part of the Longitudinal Study of Children at Risk were evaluated at early school age; after controlling for socio demographic factors in these Chicago public school children, grade retention was seen in 26.2% of the children, and special education was needed for 8.9% of the children.23
Grade retention and need for special education, which when combined total 35.1%, would be most comparable with school-readiness levels 1 and 2 (i.e. not school ready) in our cohort. In both our cohort of preterm children and Reynolds' cohort of all children at risk, the majority of the children were from the Chicago public school system.
A school-readiness measure has, to our knowledge, been used in only one previous study, in which risk factors associated with need for special education services in kindergarten were assessed in infants who had been born extremely preterm (23–28wks' gestation).20
That cohort study occurred at the beginning of the surfactant era of neonatology and revealed that 50% of children were not ready for kindergarten.
Hack et al. examined the predictive validity of the Bayley MDI at the age of 20 months on the Kauffman Assessment Battery for Children, using the mental processing composite score at age 8 years.6
The positive predictive value of an MDI less than 70 at 20 months for a mental processing composite less than 70 at the age of 8 years was 0.37. Among the children with neurosensory disability, the positive predictive value was 0.67. When we construct ROC curves using the data from Hack et al., the area under the ROC curve for the Bayley MDI to predict 8-year mental processing composite is 0.81. This is similar to our ROC analysis. However, the purpose of the study by Hack et al. was to examine the predictive value of the Bayley MDI on an overall cognitive outcome score on the mental processing composite. Our analysis was designed to examine the impact of 2-year Bayley scales on school readiness at the age of 5 years 6 months using several dimensions.
Our finding of poverty and low socioeconomic status affecting preterm infants when they reach school age was dramatically shown in the Edinburgh follow-up study.24
In that very early era of neonatology, children who survived very low birthweight and lived in advantaged households were not different from their siblings in terms of intellectual ability and educational achievement in the first grade of school. However, a combination of low socioeconomic status and very low birth-weight (<1500g) resulted in significant decreases in both intellectual ability and educational achievement.24
Several investigators suggest that the suboptimal outcomes of poverty and socioeconomic status on child development have the most impact during preschool years.25
It is in these areas between the ages of 18 months and 5 years that US children in poverty experience fragmented medical, developmental, and educational support.
In a prospective follow-up study of infants after they left the neonatal intensive care unit, Resnick et al. attempted to measure the effects of birthweight, medical conditions, and socioeconomic status on educational disabilities in a Florida state-wide sample of over 24 000 children.26
The results suggest a correlation between birthweight and requirement for special education services: 40% of children with a birthweight of 500 to 750g, 35% of those with a birthweight of 750 to 999g, and 30% of those with a birthweight of 1000 to 1499g required special education services later in childhood, compared with 24% of those who weighed 2500g or more at birth. Mild mental retardation (IQ 55–69) was most related to male sex, black race, and mother's educational achievement of less than high-school completion. Specific learning disabilities, emotional challenges, and speech and language impairments were strongly tied to socio demographic factors, especially lower family income. With the current reduction of public funding for disadvantaged urban areas and the lack of human and community resources available to medical and educational professionals serving children in these neighborhoods, the importance of comprehensive support for very- and extremely-low-birthweight children experiencing social adversity is critical.
Over 2 decades ago, Hille et al. undertook a collaborative follow-up study at the ages of 2, 5, and 9 years of 1338 Dutch infants born very preterm or with very low birthweight.27
At the age of 5 years, 12% of the cohort were receiving intensive special education services. At the age of 9 years, approximately 19% of children were receiving special education, with almost half (47%) having already been in special education since the age of 5 years. Twice as many males as females were in special education, and children from low socioeconomic backgrounds were five times more likely to be in special education (35%) than their counterparts from high socioeconomic backgrounds (7%). Socioeconomic status and sex more substantially contributed to suboptimal school outcomes than very or extremely low birthweight.
A limitation of the present study is the difficulty in obtaining greater longitudinal follow-up at the ages of 2 years and 5 years 6 months. Great effort was made to remain in contact with the families over the years, but despite this, some of the families were unfortunately unable to be reached. In addition, this was a single-center study, and the numbers are small. Lastly, even though our center works closely with the Early Intervention, Ounce of Prevention, and Head Start programs, there is not universal access to these services for preterm children.
Our study revealed that 2-year neurodevelopmental assessments of preterm infants are good predictors of school readiness. We found that abnormal 2-year neurosensory disability or delay (MDI or PDI <70) predicted the need for special education services at the age of 5 years 6 months. We also found that children with MDI or PDI scores of less than 85 (1SD below the mean) had an increased risk of not being ready for school, especially if they were experiencing social disadvantage. Our results highlight the importance of ensuring access to good-quality preschool education experiences for children at the highest biomedical and social risks, so that they can enter kindergarten ready to learn. We believe that preterm infants should continue to be followed longitudinally with structured assessments beyond the age of 2 years to allow early interventional programs to be evaluated further and to help identify factors that promote developmental resilience and educational success.