As long as clients are not commissioning you at ridiculously low prices and undervaluing the work because you are a student, I don’t see a major problem.
There are always exceptions to the “rules” it’s tough to blanket statement that “all students should not freelance”.
For example, myself and majority of my fellow students during our illustration course days, would not have been confident, professional or skilled enough to take on freelance work whilst studying.
Your work seems consistent and solid and it’s awesome that you’re getting an early start into earning a living , however if you’re still studying then I can understand an educator being concerned about allowing yourself enough time to explore and push your work forward as part of your studies. A lot of students aren’t mature enough to juggle this.
On my course - our tutors were very much about breaking our perceptions of how we SHOULD draw, and wanted us to explore and expand our thought process, so much so that I feel some of my university work is still BETTER than a lot of my current freelance art because I was genuinely experimenting and not playing ‘safe’.
And then on the other side, you’re actually making money and producing nice work which gives a whole other giant ton-load of experience which you would never get by “just” studying.
That’s my personal opinion as a practicing creative. Would be awesome to hear from a teacher’s point of view.