Broad View of your Network
From a birds-eye view, a school network is a single point where internet traffic comes on or goes out of the school, which then passes through filters, and then connects to local servers (computers offering services to other computers on the local network) and all devices. The connection to many modern devices is wireless, but there are still wires from the internet to the on-site router to a switch to a WAP (WiFi access point). Most schools have multiple switches and WAPs with wiring connecting all of them.
Let's start with the router. Yes, the black box the ISP (Spectrum for most in Brevard) sets up is a router. It is the same router you have in your house. Is it efficient enough to handle 300 devices at once? Surprisingly, yes! But I don't know of any school that uses it. You do not have full access to it, which may result in a conflict. Most schools use a UTM (Unified Threat Management) box that serves as a router, firewall, content filter, DNS, DHCP, and offer add-ons for things like antivirus, remote VPN connections, and device management. The cost a bit up front, have an annual fee for services, and are a single point of failure. Bot they offer a lot and often come with an overnight replacement policy if they go bad. A business class router / firewall that is not a UTM will cost less up front and have a small annual service fee, but you may need to buy other devices or services from other companies.
VLANs start at the router, so this is a good time to bring those up. These work for free from the router, but you will want modern switches and WAPs to utilize them. If your network keeps growing bigger and bigger, you want to section off network chatter between devices for functionality and security. For enterprises, this has been standard practice for years.
A lot of the expenses have come down over the years.