Table 1.

Sample characteristics.

	Montessori (n = 70)	Control (n = 71)
Age at Time 1	41.31 months	41.00 months
Gender	39 Male	38 Male
Household income	$73,208	$68,914
Income range	$0–180,000	$0–200,000
Mother education	6.70 (1.30)	6.64 (1.12)
Father education	6.37 (1.38)	6.13 (1.23)
Ethnicity: subsample percentages
Caucasian	48%	37%
African–American	17%	15%
Hispanic	16%	23%
Asian	3%	4%
Multi-ethnic	16%	20%

Age at subsequent test points: T2: +6 months; T3: +18 months; T4: +30 months. There were no significant group differences in any demographic variable, nor was there a difference in inter-test interval time, as indicated by t-tests. A Chi Square test revealed no significant sample differences in ethnicity (p = 0.63). Income: In both subsamples, 35% of sample < $50K household income; 80% < $100K. One family declined to state income. Parent Education: 1 = less than 9th grade, 2 = 9th grade, 3 = 10th grade; 4 = 11th grade, 5 = High School diploma, 6 = some College, 7 = College degree, and 8 = Post-graduate education.