Indeed, if you want to find a good job after graduation, an excellent academic degree is essential. But on the other hand, for those who can easily get high marks in exams, it is worthwhile to try to find something to do in their spare time. Then they can gain some work experience, which is as valuable as their academic achievements.
From what I have said, it is difficult to judge whether part-time job is good or bad. It depends on how you handle the relationship between work and study. If you can balance it well, you will certainly gain enough knowledge while working.