Table III.

Multilevel Predictors of Academic Achievement

	Model 0	Model A	Model B	Model C
Intercept, β [95% CI]	97.1 [94.7, 99.3]***	99.4 [96.8, 101.8]***	104.9 [97.9, 111.9]***	100.1 [92.3, 107.8]***
Fixed effects
Individual characteristics
Birth weight statusa	−7.6 [−10.5, −4.7]***	−6.4 [−9.3, −3.5]***	−5.9 [−8.5, −3.3]***	−6.4 [−8.9, −3.8]***
Male sex		−5.0 [−8.1, −1.9]**	−4.6 [−7.4, −1.9]**	−4.3 [−7.0, −1.6]**
ADHD symptomsb		−9.7 [−14.3, −4.9]***	−7.2 [−11.6, −2.9]**	−6.9 [−11.2, −2.7]**
Family characteristicsc
Educationd			−8.3 [−11.1, −5.5]***	−7.6 [−10.5, −4.8]***
Black racee			−3.9 [−7.2, −0.7]*	−2.2 [−5.7, 1.2]
Unmarried			−2.1 [−5.1, 0.9]	−1.0 [−4.0, 2.0]
Parental protection			−0.4 [−0.6, −0.1]**	−0.3 [−0.6, −0.1]**
Neighborhood perception			−0.01 [−0.1, 0.1]	0.04 [−0.1, 0.1]
Neighborhood characteristics
Poverty ratef				−0.2 [−0.3, −0.05]**
High school dropoutsf				−0.1 [−0.2, 0.2]
Random effects
Between-tract variability	58.4 [33.6, 125.3]***	53.9 [31.3, 114.0]***	30.1 [15.3, 84.3]**	30.5 [15.7, 82.0]**
Within-tract variability	163.5 [132.6, 206.7]***	151.3 [122.9, 190.8]***	127.2 [103.9, 159.3]***	123.5 [100.9, 154.7]***
Variance explainedg
Between-tract variability	0	7.7%	48.5%	47.8%
Within-tract variability	0	7.5%	22.2%	24.5%
AIC	2952.9	2904.6	2810.2	2806.1
Model comparisong		48.3	142.7	146.8

Note. CI, confidence interval.

^aELBW versus NBW.

^bRefers to parent ratings of ADHD symptoms—inattentive, hyperactive–impulsive, and combined types (Gadow & Sprafkin, 1997).

^cUnless otherwise stated, refers to the primary caregiver, which was the biologic or adoptive mother for 164 children [90%] in the extremely low birth weight group and 157 children [89%] in the normal birth weight group.

^dPrimary caregiver education of high school or less.

^eWhite race includes two Asian ELBW and two Asian NBW children.

^fAccording to 2000 US Census.

^gRelative to Model 0.

*p < 0.05; **p < 0.01; ***p < 0.001.