In Prison Architect, can external staff members (e.g. teachers) access Staff Only areas

Via Bureaucracy, research "Deployment":

This requires a Warden - to unlock the Chief - the Chief, and offices for both.

Once unlocked, you get access to the Deployment tab in the menu bar, which offers a bunch of selections:

There, select "Staff Only", and click on the area you want to change:

This means that only staff are allowed to enter this area (in this case, the Chief's Office) on their own - Guards can still escort prisoners through these areas, and staff will not avoid secured areas, just because a staff only route is available.

As such, yes, it can be used to prevent escapes (hints from the Deployment wiki article:)

• By designating areas such as the kitchen, and the corridors leading up to it as staff only, you can greatly reduce the amount of knifes stolen. The same principle applies to storage.
• If you have fenced off your entire prison, you could designate the entire area inside and outside the fence as staff only to isolate cell blocks from eachother. Do remember to provide passage to canteens and showers if these are in a seperate building.

Also: This is not a new feature of Alpha 10. Alpha 9 introduced the new Jobs feature, but this has existed for a while before already.

It sounds like Fog of War is actually turned on. To fix this without having to start your prison from scratch:

• Navigate to your save folder (which you can open from within Prison Architect, or the default path is C:\Users\<User Name>\AppData\Local\Introversion\Prison Architect\saves)

• Open the .prison file of your prison in Notepad, or your preferred editing program (make sure you're not running Prison Architect while you edit this file)

• Look for the line EnabledVisability = true and change it to EnabledVisability = false. (There are a number of other things you can tweak in this file, like giving yourself extra money - Introversion deliberately made this easy while the game is in alpha, because it's not 100% balanced yet)

• Save the file, and re-open your prison

To answer your other questions, yes CCTV would also fix this problem (so long as you had a guard within range of a CCTV monitor). To get a guard to remain in a room, you need to unlock "Deployment" in the Bureaucracy menu (this requires a Warden and a Chief). Deployment allows you to station guards in specific rooms - useful if you have a lot of prisoners in the same place at the same time, such as the canteen. If you want your guards to stand in a specific spot in a room (such as beside a CCTV monitor) you can also designate patrol routes from the Deployment menu.