Yes stress can have an impact on our blood glucose...
Has the body releases stress hormones it effects our blood glucose, in general they go upwards but it's possible if you are shocked your levels can dump instead..
As for your driving lesson's it's going to be difficult to determine which is the best way to go, because last thing you want is to inject to over compensate for the stress kick, and give yourself an hypo... I'd been tempted to change the time of my driving lesson to before a meal... And keep an eye on what's happening then hopefully if you get a raise for stress before the meal be less impact and easier to correct etc...