Hey guys,
I've set-up internal network in local school and everything works like a charm until local computers decides to update Windows OS. Main problem is bottleneck on ISP side (30M/30M).

Could anybody tell me how to solve this problem without spending ton of money? I was thinking to use core Router (CCR1009-7G-1C) as Proxy server so it could download Windows Update once and all other devices would downloaded from there. Or is there a better solution? I don't know how to do it so any advice/manual or even link would be much appreciated.

i will suggest you setup a firewall rule to capture the destination ip address of the server responsible for the update and setup a firewall rule to drop traffic to the server so as to make use of the internet service.
hope this will work????

Shouldn't they have a WSUS server for centralized update management?

i will suggest you setup a firewall rule to capture the destination ip address of the server responsible for the update and setup a firewall rule to drop traffic to the server so as to make use of the internet service.
hope this will work????

I can do that no problem, but their teacher of IT (he's not much of an IT imho, lol) wants computers to be able to update which is fine, but the problem is that it's a school and those Windows OS devices aren't online ever day. I explained to him that he would need WSUS server, but they don't have capital for that.
I have setup networks for city police departements, municipal bureaus and there weren't any problems because these departements have capital and even without it they use their computers everyday, so updates are more "spreaded out" and won't happen all at once.

Anyway I'm thinking blocking connections for windows update on bussiness days and he can do windows update on weekends. I was just curious if anyone here dealt with the same situation and have some low costing automated solution.

Shouldn't they have a WSUS server for centralized update management?

Sadly they don't have money to buy a server.

Depending on version and edition of Windows they use, you could look into:
Delivery optimization https://docs.microsoft.com/en-gb/window ... timization
There is also something called BranchCache https://docs.microsoft.com/en-gb/window ... ranchcache but I think it requires WSUS