Parents of young kids: How much time did you spend reading to your kid(s), helping them with homework, and ferrying them to educational activities yesterday? If your answer is “about an hour,” you’re close to the American average—and probably outstripping your own parents. If you devoted more than an hour to educational activities with your son or daughter, and still fear that you’re not doing enough, you’re likely college-educated.

The popular stereotype here is of middle-class moms enrolling their toddlers in foreign language classes in hopes of sending them to Harvard someday. College-educated parents do spend more time on educational activities than less educated ones, but Americans of all socioeconomic backgrounds have come to allocate more time to such activities over the past few decades. In fact, in 2008–2013, mothers with no more than a high school diploma devoted more time, on average, to developmental child care than mothers with bachelor’s degrees did in the early 1990s (57 minutes a day versus 44).

Yet the “parenting gap” between social classes isn’t apt to close anytime soon, a new Journal of Marriage and Family article implies. Evrim Altintas of Oxford’s Centre for Time Use Research looked at data from the American Heritage Time Use Study spanning five decades, and discovered that despite positive trends in all groups, the disparity in educational child care between parents from different educational backgrounds has grown over that period.

The gap between mothers with only high school degrees and those with bachelor’s degrees, which was negligible in the 1970s, reached more than 30 minutes in the early 2000s, then narrowed somewhat to 21 minutes in the late 2000s. In 2008–2013, college-graduate mothers spent 78 minutes on developmental activities with their kids, while the figure was 62 minutes for women with some college education and 57 for those with a high school diploma or less. For fathers, the gap between the highest and lowest education groups is now around 15 minutes (55 minutes versus 39). In the most recent time period, at every education level, mothers devoted roughly 20 more minutes per day to developmental child care activities than fathers, on average.

Accounting for the fact that children with less educated parents are more likely to live apart from their fathers makes these gaps more dramatic. According to Altintas’s estimation, which she notes is if anything biased downward, once fathers’ residential status is taken into account, children of parents with bachelor’s degrees may receive more than 1,000 extra hours of cognitively stimulating care over the first four years of life, on average, relative to children with high school–­educated parents.

Altintas believes “the growing inequality in parental time investment reported in this research is alarming and most likely underestimated.” As she warns, the worsening disparities between children from different backgrounds—in educational time with parents, household income, family stability, and more—“undermine equality of opportunity and contribute to the intergenerational transmission of parental (dis)advantages.”