This is a revision on the previous advice.
There have been a couple of incidences in the past where, for a variety of reasons, we have found ourselves operating without the airspace being opened. The onus for opening the airspace now rests with the duty instructor. So check with him/her before commencing operations.
I suggest you write on top of the tug card the airspace given. If the airspace changes during the day this should also be written on the card along with the time of change.