Researchers studied 1,300 children from birth and assessed them 13 times between the ages of one month and 15 years.
They were observed at their childcare settings five times between the ages of 6 and 54 months.
The children were born in ten cities across the United States and came from a cross-section of middle-class, low-income, two-parent and single-parent families.
The study, 'Do Effects of Early Childcare Extend to Age 15 Years?', published in the journal Child Development, found that higher quality daycare is linked with higher levels of academic achievement, and that the level of achievement increases with higher levels of quality. However, children who spent more hours in daycare during the first four and a half years of their lives showed more risktaking and greater impulsivity at age 15 than teenagers who spent fewer hours in care.
The report concludes, 'To the extent that early childhood quality increases cognitive-academic skills, it will be important to learn whether subsequent educational attainment in high school and beyond is related to early child-care experience.'
The study also recommends that the teenagers are reassessed in late adolescence to investigate the effect of daycare on risky behaviour at a later age.