Andy,
I commend you for taking on an Apprenticeship in the first place.
I'm not willing to "stand on" anyone here, I've done 2 of them, the first as an Electrician and the second as a Lineman.
No one is saying for a second that an Apprenticeship is an easy thing to go through, but ahh, the spoils at the end of it!.
And as an Apprenticed, Fully Qualified Electrician, your chances of getting employment around the place are a lot better.
Naturally, if hired somewhere, the first question will be, "where did you serve your time?."
At the same time, use the time that you have in Night School to your advantage, it is of more use to you than any book that you will ever read, it's right there, if you don't understand something,
ask!.
I've had a few Apprentices under me in the past and one thing that doesn't wear well with me, is a lack of basic Electrical Theory, it's essential for Fault-finding and also Installation work, regardless of how good your Mechanical skills are.
Suck it up while you can.
Just as a note, even though I'm doing mostly High Voltage stuff these days, I never fail to keep up with the Low Voltage and Electronics developments in the Trade these days, to not do that, would mean I would be eventually left behind and I don't want that to happen.
Best of Luck, Andy!!.