Final answer:
The most helpful addition to the school building's network would be a repeater. A repeater amplifies and extends the signal in a network, improving coverage and network performance.
Step-by-step explanation:
The most helpful addition to the school building's network would be a repeater. A repeater is a device that amplifies and extends the signal in a network, allowing for better coverage and improved network performance. By adding a repeater, the signal strength and reach would be increased, reducing buffering and long download times in the affected classes.
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