The most helpful addition to the school building’s network for addressing issues with buffering and long download times would be a repeater.
A repeater can help strengthen and extend the signal over longer distances, improving the overall connectivity and speed of the network, which can lead to better performance for video streaming and downloads.
The other options, such as POP protocol (which is related to email retrieval) and stack protocol (which is not a standard networking term), would not directly address the buffering and download speed problems experienced with video streaming.