Children from higher-income families are more likely to attend afterschool facilities, with this gap widening over time.
New research published by the Economic and Social Research Institute (ESRI) found that higher-income families are more likely to make use of childminders or group-based childcare.
A study looked at changes in afterschool care over a 10-year period, comparing children born in 1998 to those born in 2008. It analysed outcomes for children at ages nine and 13.
Over that decade, the cost of afterschool care increased at a rate higher than inflation, particularly for childminders and afterschool centres or clubs.
Of those born in 1998, 24pc were in non-parental care during the school term, compared to 29pc of the group born in 2008.
Maternal employment was found to be the strongest predictor of afterschool centres, while childminders were most commonly used by parents with the longest working hours.
A number of different outcomes for children were identified by the study. Children cared for by a childminder or afterschool centre were more likely to be involved in sport at age nine.
Children being looked after by their relatives or siblings did less reading for pleasure and were less likely to participate in cultural activities like music lessons.
Nine-year-olds with childminders or in centres spent less time online or watching TV. The difference was smaller among 13-year-olds because almost all of them owned mobile phones.
Among the age 13 group, those cared for by relatives tended to have fewer friends and close friendships than their peers, with "constrained access" to their network of peers being a potential explanation.
Similar to the younger group, the 13-year-olds in the study were more likely to be involved in sport if they were looked after by a childminder or afterschool centre.
There were also different educational outcomes, with 13-year-olds who were cared for by a childminder at age nine scoring higher on reading and mathematics tests. Vocabulary test scores were lower among 13-year-olds who were being looked after by their relatives.
"The study findings have important implications for policy development," report co-author Dr Helen Russell said.
"Evidence of rising costs over time suggests that choice of afterschool care is constrained by income, with relative care remaining an important support for less advantaged groups.
"The largely privatised nature of the system has led to geographical variation in provision, with childminders playing a more important role in rural areas."
The study highlighted that afterschool services "have the potential to enhance children's development".
However, higher levels of behaviour like conduct or hyperactivity issues were found in group-based settings. This was described as "concerning", with providers being encouraged to focus more on developing children's interpersonal and coping skills.