I live directly opposite a school. When I work, I leave for work at 8 am and am back at 6.30pm. Obviously no problems with this during these times.
However, about 6-8 times a year there are some parents evenings or school events after school in the evenings and parking is awful, i have to park about a 10 minute walk away and work out how to get nursery bags, food shopping, work bag and a toddler/baby to my house with no pushchair as had no idea there would be an event on. Not fun.
When Im not working and have to take Dc to preschool nursery, I need to plan to get my car off driveway to park on the road much earlier than I need to as sometimes, very rarely, I might get blocked in on my own drive or the parents give me no room to reverse and turn my car off drive as they park so close to each side of my drive.
Our local council parking officers frequently loiter around handing out tickets for stupid parking.
All in all: I've mellowed a lot over the years. Used to get very irate and anoyed but its not as awful anymore, just more used to it.
I also think the school advise parents to arrive no earlier than 15 mins before dropping off and picking up time to limit congestion times on the road. Really, it affects me for 30/40 mins max per day.