User Manual Philips SBT75WHI/37 Wireless speaker

Kinda depends on the people, how much noise they will be making, and the room, and the power of what is paired with it.
This worked well for my wife, using her iPad Mini 2, to play accompaniment tracks for her music class, of up to 18 kids, 1st grade through 6th grade. However this was in a room with almost no padding, wood floors, so that really echoed sound well. If there is a lot of padding around, soft stuff, then it might not do so well.

No, sorry, can't plug in a flash drive. It connects through bluetooth, so any smart phone or laptop should be able to connect to it. Pros: it's a decent sound for the cost and the battery lasts for a while. Cons: not loud enough (if a lot of other stuff is going on around), sound cuts out intermittently when the battery starts to get too low.

Mine did not come with a plug for a wall outlet. You can charge it from a wall outlet, but you have to provide your own adapter.