Preschool could mean around 2-4 in the states at the time (about 20 years ago, I guess. We didn’t have to do it for our younger guy, we had then-unemployed-me, and a flowing cache of stored mommy milk when he was a baby, and then the Montessori school his mom was working at when he was older).
Still feeding? And you left your child there? You monster! JK, adults have to work, and it sucks.
I had to do that, too. You’d think leaving him with relatives rather than a stranger would be better, but I know my relatives, quite well, and it was often a toss-up.