Why wifi does not support high user densities and how to fix it.
WiFi uses a collision mechanism to control access to "the air" (csma/cd)
This means that devices must first listen to the air, they may transmit if they hear that no one else is transmitting, they must then listen to see if any other device decided to transmit at the same time, and if they did then a collision has occurred, the packets become corrupt and are wasted.The devices must retransmit the packets.
WIth few devices there are few collisions and few wasted packets.
As you get more devices on an AP there are exponentially more collisions, and exponentially more wasted bandwidth.
A wi-fi network with 10 devices on an AP may be 5% efficient.
In a class environment the teacher says "log-in" this is a command for all devices to transmit at once, the result is a storm of collisions, retransmissions, more collisions.