Hitting children in general is no longer encouraged though a great many parents still don't mind the use of a hit now and again to deal with an unruly child. Hitting someone else's child is almost the worst thing you can. It seems to offend another parent's sensibilities, especially if they're not into smacking, which is fair enough.
I hit another person's child once. I was 14 and had been babysitting for the local neighbourhood for years. Although I was young I was a good and trustworthy babysitter. I could change nappies, give babies bottles, tuck toddlers into bed, play games and entertain children, tidy up after children, feed children and tidy the kitchen. I didn't bring boyfriends over, ignore the children or spend time on the phone. I did a honorable job making sure the children were safe and happy in my care.
One family I had worked for, for around a year, had a daughter around 10, a boy 8 and a baby, around 12months. Every afternoon after school I would go around to their house and mind the children until the parents came home around 6:30pm - 8:30pm. Either the dad or the mum had collected them from school and waited until I arrived before giving me instructions, then leaving me in charge. Sometimes I minded the children while the parents went out on dates.
The instructions might be things like they needed to be in bed by x time, don't give them any this or that, prepare their dinner, help with homework.