Here, most schools have analog crap that looks like it was installed by fly-by-night guys. Seriously though, I think the janitor does it in my daughter's school. Depends on budget. If there's money involved then for larger businesses/gov't it's what zero-degrees said. I see mostly Axis/Bosch with some Avigilon thrown in. If you have to ask how much, you can't afford it...
As for "turn-key", there's no such thing really. There's always training with even simple to operate systems, even after the hard stuff is done, like getting written requirements of how the system is supposed to perform. Clear plates day/night at the three entrances. Sharp facial shots with 150ppf at 8 entrances day or night. Overview cams covering which areas? Retention times for video. Etc etc. "Turn-key" usually means a cheap plug and play DVR or NVR with wideangle cams used universally with poor results.