19thcentury 20thcentury babysitters care child childcare childcareservices childdevelopment childhealthservices children childrenofworkingparents childrenwithsocialdisabilities chronicallyillchildren chronicdisease chronicdiseasesinchildren congresses daycarecenters diseases education education(elementary) education(preschool) efficiency employer-supporteddaycare england headstartprograms healthandhygiene history industrialproductivity interactionanalysisineducation kk4933 nurseryschools organizational poverty preschool schools socialization socialsupport special standards unitedstates w3hy9454th1977s wa11aa1s8w1973 wa320c4391992 workandfamily