If you are using BitLocker as a way to enforce a policy that all USB removable drives are encrypted or disabled, you will not be able to access the micro:bit. Microsoft advise that there is no feature to conditionally do BitLocker encryption on removable storage – either you require it for USB attached (i.e. removable mass media) storage, or you don’t. So, to work with the micro:bit, the teacher would have to ask their IT Admin to turn off BitLocker removable storage encryption. [Source: Microsoft, 21 Oct 2016]

Whitelisting devices

A workaround is to exclude all USB devices from connecting unless specifically whitelisted (micro:bit, keyboard, mouse etc)

(but note that endpoint encryption has to be turned off for the micro:bit to work).

If you are using policy enforcement software other that BitLocker, you might be able to provide a whitelist based on the devices USB VID and PID identifiers,  although specific policy enforcement software may or may not support this whitelisting by VID and PID, you would  have to check with your network administrator.

Using WebUSB

Another option to mitigate the issue with Bitlocker is to make use of theWebUSB functionality built into the Google Chrome Browser.

Further information

exclude certain usb hardware id from BTG policy