The sensor socket that ships with the bit:bot is really fragile - in class we had 6 out of 10 break off through fairly normal wear and tear. The design fault is that the socket is right in front of the micro:bit socket - inserting the micro:bit and/or cable stresses this socket.
I would recommend the soldered sonic ALONG WITH the 90 degree usb adapter for classroom situations - seems way more robust on what otherwise is a pretty snazzy device. can you order them up-front with this combo? If not, why not?