I think its all relative, or at least for me anyway. I'd be/am proud of anything my son achieves to his full potential. For example if he excels in school/college & Uni achieves high in his education and then he decided to become an apprentice spark (no disrespect) but I think I would feel a little disappointed. I think it's just that I would want the best for my son and would like to see him achieve much more than I ever did. If I was to choose my career over, then I very much doubt I'd be a spark. Even though I do enjoy some of the work I do, I've sort of "made do" for the most part just to earn a living.
I envy those folk who "love" their work.
But ultimately my Son's own happiness is all that really counts, so if being a sparky made him happy then I would be proud he was. Its a good respected trade to have with a lot of responsibility and requires a high level of intelligence, just a shame the earnings don't always reflect this.