Table 1.

Demographic characteristics and descriptive statistics for all children in Beijing, Guangzhou, and Jining

	Beijing		Guangzhou		Jining
	Grade 4	Grade 5	Grade 4	Grade 5	Grade 3	Grade 4	Grade 5
No. of children	263	203	250	227	1,262	1,322	2,324
No. of boys	146	109	145	114	669	714	1,288
No. of girls	117	94	105	113	593	608	1,036
Mean age in months (SD)	114.55 (4.58)	126.90 (5.50)	121.71 (4.22)	134.21 (4.72)	110.18 (5.38)	121.80 (6.14)	133.83 (5.08)
No. of children administered the nonverbal IQ test	262	203	248	226	1,222	1,247	1,209*
Mean nonverbal IQ in percentile (SD)	75.02 (21.16)	73.08 (23.52)	67.94 (25.15)	70.71 (24.66)	72.31 (24.51)	68.64 (23.78)	70.45 (24.40)
No. of missing data (date of birth, reading score)	—	—	2	1	21	44	4
No. of children with nonverbal IQ below 25th percentile	21	25	38	32	152	154	165
No. of children in the final sample	241	178	208	193	1,049	1,049	1,040
Mean character-reading score (maximum = 300 for Beijing and Guangzhou and 250 for Jining) (SD)	63.31 (30.62)	100.92 (45.44)	64.87 (33.75)	89.88 (48.46)	71.56 (24.43)	79.84 (30.93)	102.79 (38.92)

SDs are shown in parentheses.

*One primary school in Jining was cooperative in giving us time to administer the reading test to its 1,115 children in grade 5 but had difficulty giving us time for the nonverbal IQ test. So, in the final sample, the children’s data from that school were not included. However, we performed an independent analysis of the incidence rate of reading difficulty in that school and found that 55.61% of children had reading scores that were two grades behind the expected reading level. This percentage is quite similar to what we have obtained from another five schools.