I would have liked a third answer choice. Most likely, it shows the educational level and economic status of the parents. 28 years ago, not everybody went to preschool, and preschool rarely lasted more than half a day. Families where both parents worked would either have had to have someone pick up the kid from preschool -- either one of the parents or a paid caregiver. This person would have then spent the rest of the day focused on the child, and parents who could afford these options probably also had educational toys at home, etc. Parents of middle or lower economic brackets would not have been able to afford either of these options.

Both parents would have had to work, and then their kid would have gone to an all day "daycare" instead of a half-day "preschool". The difference is that while kids are looked after in a daycare, 28 years ago, not all daycare centers had any educational activities at all, and there was not a lot of regulation to make sure there was any. Now they are more regulated in terms of how many kids they can have per caregiver at different ages, nutritional value of food served, and activities provided. Then, they might have been crowded, or it could have been a neighborhood person that watched tv while the kids played. I think if you followed kids in preschool/daycare now, the difference would not be as striking.