Both of my kids worked during college term time, other than their first year. Both had worked in high school, too. They also did a significant amount of unpaid work in connection with extracurriculars and their interests.
Apart from furnishing essentially all of their discretionary spending money, the work was important to them in various ways. For both, some of it was career-related. My daughter initially intended to pursue a career in journalism, and she made sure she had a lot of paid and unpaid journalism, editing, and publishing on her resume. (Then she changed her career path, but that happened mainly after graduation. Her college’s career office used her work plan – and her modular resume that easily generated five or six different versions emphasizing different strengths and skills – as a model for humanities students.)
A good deal of her social life also revolved around one of her part-time gigs, working at a coffee shop in what was effectively the student union building, that a group of friends including her effectively took over and ran for three years. It was their clubhouse. (She’s been out of college for almost 10 years, and the guests at her recent wedding included 7 people who had worked at the coffee shop.) At one point – and without our permission, as if that mattered – she had four regular part-time gigs for the university, and she was working enough hours per week (25, I think) that she qualified for benefits. Of course, that triggered an alarm somewhere, and her hours were quickly capped.
My son’s main job related to one of his principal extracurricular activities. He was paid for 10 hours/week, and actually worked probably 8-25 hours, depending on what was going on. (There were many more 20-hour weeks than there were 10-hour or less weeks.) After his junior year and during his senior year, he also had a paid part-time job working in a lab related to his major, and he did unpaid editorial work on an academic journal in his field.
Did it affect their grades? Maybe, a little. There’s no question it affected their happiness, though, in a positive way. They got paid, of course, but they also got praised, they felt competent, they developed and used skills that weren’t valued in academic courses, they met challenges, overcame them, and were proud of the results.