Try VNC Single Click https://www.uvnc.com/products/uvnc-sc.html you do all the configuration on your side, port forwarding and static public IP address or dynamic DNS service. Once. You are welcome (I'm that confident that'll love it like I do). You can even rename it do.zip and extract the files (logo, config). I don't recall trying to update the config and put it back in the zip and renaming it back to .exe.
is it your pc or the schools? are you in the same physical location and have admin access to the pc? You could install vnc and use the view only function. that is free software and easy to install and use
This is an old thread but thought I'd weigh in. For a small shop like you describe - I would recommend building your own remote agent - its not hard and you can build one quickly and brand it with https://www.uvnc.com/products/uvnc-sc/78-ultravnc-sc-online-creator.html - I started out using it and then moved onto a RMM myself but if you are looking to just be able to remote into a small number of pcs then it will fit the need. It will work thru firewalls and the client initiates the connection by clicking an icon. Doesn't need to be installed as it builds a portable exe and you can even build out like 3-5 sessions if you have some employees that will help with tickets etc.
Not my words, but still true:
"UltraVNC. The open source software, UltraVNC is an excellent alternative to TeamViewer for Windows users. It was developed and distributed under the free GPLv2 license. The software bundle from viewer (client) and server (remote PC) helps you to set up and manage remote connections"
The code for ThinVNX is FOSS, but not maintained (UltraVNC's popularity caused it's abandonment).
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PS: GPLv2 license = Free for any form of use, private, public or commercial, REGARDLESS of TOS/EULA (as GPLv2's terms supersedes that)
I use VNC and bginfo. Customers give me their IP address from their desktop and I connect. Worst case you can talk them through getting the IP by hovering over the vnc icon.
https://www.uvnc.com/products/uvnc-sc.html is another option for a click to run support application based on vnc. They run that, it phones home and you are connected.
That said I haven't used it.
The built-in screen sharing lets you make the screen smaller, but not bigger. It's quite stupid.
You can set up VNC access (System Preferences -> Sharing -> Screen Sharing -> Computer Settings -> VNC viewers may control screen with password) and then use Chicken (formerly "Chicken of the VNC") or other VNC clients, like UltraVNC on Windows.
Or use TeamViewer, which is also cross-platform.
uVNC supports Windows auth https://www.uvnc.com/features/authentication.html#mslogon2 you restrict remote control to AD groups. Problem is the password is restricted to 32 chars, it can't handle larger ones