Table 5.

Fixed Effects From the Cross-Classified, Growth-Curve Model for Total Number of Years Students Were in ISI Intervention Classrooms for Reading Score (z score)

Effect	b	b SE	t	p
Fitted mean, θ0	0.204	0.033667	t(2911) = 6.055	<.001
Total ISI, γ01	0.060	0.026434	t(880) = 2.279	.023
Time, θ1	0.037	0.002315	t(2911) = 16.159	<.001
Total ISI, γ11	−0.004	0.001568	t(2911) = −2.656	.008
Time2, θ2	−0.0005	0.000156	t(2911) = −3.178	.001
Total ISI, γ21	0.0001	0.000106	t(2911) = 1.092	.275
Time3, θ3	0.0001	0.000010	t(2911) = 13.368	<.001
Total ISI, γ31	0.00002	0.000007	t(2911) = 3.429	<.001

Note: The fitted mean, θ₀, represents the fitted mean end-of-second-grade score for students who were in control classrooms all 3 years. Time is in months and is centered at the end of second grade. Time² represents the quadratic trend, and Time³ represents the cubic trend. Total ISI, γ₀₁, represents the number of years (1, 2, or 3) that students were in Individualizing Student Instruction (ISI) classrooms. Total ISI, γ₁₁, is the effect of ISI on the slope; Total ISI, γ₂₁, is the effect of ISI on the quadratic trend; and Total ISI, γ₃₁, is the effect of ISI on the cubic trend.