CTL: There are teleconferencing services (including some free ones) that do have the ability for the host to mute everyone and selectively unmute specific callers.
Regarding computer labs, the very heimish very in-town yeshiva I’m familiar with had a computer lab for the elementary school at least 40 years ago. (Probably even longer.)
Btw, the SAT and ACT are planning to offer at-home remote exams for the upcoming tests, due to social distancing restrictions possibly still being in effect.
T1 lines are ancient. Today’s FiOS and cable modems are faster than a T1.