Adel In that case, I understand that you want to serve all 80 students at the same time. The built-in wi-fi in the Raspberry Pi can't handle' that load. The MoodleBox would handle 80 users through an external wireless access point connected to it through the Ethernet cable. The access point could be the one built in to a (the) home router. There were similar discussions in this forum, see for example https://discuss.moodlebox.net/d/230-max-wifi-connections-rpi-only-or-rpi-router. Of course the assumption is that the external access point can handle 80 connections, which I don't know.
BTW, it is not a firmware "issue". Wireless connections need physical power (mW). Any transmitter has an upper limit. In the case of wi-fi the power sets an upper limit on the number connected devices. Whether it is 10 or 30 in the case of RPi is a matter of tuning, trading raw numbers against features. But 80 is too far even with zero features for the tiny RPi.
Yes, for 80 students opening a quiz in the same second, I would take a powerful RPi - a 4B starting at 4 GB RAM would be safe I think.
I didn't understand 100% what your classroom is. You want a portable LMS + quiz engine, I assumed. Yes, R Pi is portable indeed. The limitation for your class is its size, i.e. the number of wi-fi devices. If there is a router in the classroom with built-in access point which can handle 80 connections, worth exploring that possibility.