Late to the conversation, but I'm of the opinion that the student shouldn't walk. They had two years to pay off the fees. Yes, I understand a parent recently lost their job, but as OP has provided, this seems to be a consistent issue with this family for years.

With that being stated, I would have escalated this to my administrator months ago so they wouldn't be surprised. If they told me to drop it I would. I can't fault an administrator for letting the kid walk. Not worth the drama.

On a sidenote, are bands fees really $1800 these days? I left education a decade ago but that seems EXTREMELY high.