Yes I do agree with you that piracy is not a good option, and if the hypothetical student did indeed have zero budget and enough moral character to refuse to pirate the commercial software, then open source would be the ideal choice in this situation.
By using open source products in education in the first place, you can push students to install the same software at home and continue tinkering. Without regard to their material status or moral character.
I don't see why you demote this to merely an option. It's the cruical selling point. Open source programs also tend to be cross platform (available to more students) and support open data formats (their data will not be locked, flowing freely).
