Control group

N = 480

Intervention group

N = 518

N (%)

N (%)

P

Gender

Boys

259 (54.1)

267 (51.8)

0.482*

Girls

220 (45.9)

248 (48.2)

Nationality

Greek

375 (78.3)

429 (82.8)

0.070*

Other

104 (21.7)

89 (17.2)

Age (years), mean (SD)

4.6 (0.5)

4.6 (0.5)

0.368**

Comprehension of the spoken language

None to moderate

74 (16.0)

61 (12.1)

0.082*

Very good/Excellent

388 (84.0)

442 (87.9)

Ability of speaking the language

None to moderate

113 (24.5)

117 (23.4)

0.700*

Very good/Excellent

349 (75.5)

383 (76.6)

Father’s educational level

Primary to high school

338 (80.7)

375 (75.6)

0.066*

2-year college/University/Post-graduate studies

81 (19.3)

121 (24.4)

Mother’s educational level

Primary to high school

309 (73.0)

328 (66.1)

0.023*

2-year college/University/Post-graduate studies

114 (27.0)

168 (33.9)

Parents living together

No

24 (5.1)

18 (3.5)

0.240*

Yes

451 (94.9)

491 (96.5)

Family residing with grandparents

No

379 (83.7)

404 (82.8)

Yes

74 (16.3)

84 (17.2)

0.719*

Number of siblings

None

91 (19.2)

64 (12.5)

0.002*

One

215 (45.3)

219 (42.9)

Two more

169 (35.6)

228 (44.6)

Birth order

First

265 (55.9)

247 (48.3)

0.031*

Second

152 (32.1)

204 (39.9)

Third or above

57 (12.0)

60 (11.7)

Kindergarten located in the same premises with primary school

No

404 (84.2)

472 (91.5)

<0.001*

Yes

76 (15.8)

44 (8.5)

Kindergarten’s operating hours

Classic

345 (71.9)

395 (76.6)

0.092*

All-day

135 (28.1)

121 (23.4)

Number of students, mean (SD)

16.8 (3.0)

16.5 (3.4)

0.141**