Is it ethical for a lecturer to require students to purchase an online learning kit where kit is used for course assessments?

I'll start with

How may I fight for our rights as students on this issue?

For one, politely express your displeasure to the professor.

Some professors aren't in tune with the cost of textbooks, and may not realize what a burden it is to shell out $90 for their course, when it's $90 that you can't recoup by selling back the text, or avoid by using the library's copy of the text.

They may even think they're doing you a favor by offering this "interactive" system, not realizing that you don't find it useful.

If the professor isn't interested in hearing what you have to say, you can further express your displeasure in the end-of-course evaluation (my university's specifically ask about the textbook) and possibly in a respectful letter (signed by your classmates) to the department chair.

Is this ethical? Wait, is it even legal?

As the other answers have pointed out, it's not universally considered unethical or illegal.

As unpleasant as the result is in this case, it probably would not be a good thing to set too many bureaucratic rules on what textbook or other educational resources a professor can assign. Given that the cost of tuition is usually many times higher than the textbook price, it is generally desirable for the professor to assign the textbook that will (in his/her opinion) offer you the best educational experience and therefore, the best return on your tuition investment.

Of course, students tend to appreciate when the professor can find a low-cost option that is also educationally sound. But that's generally considered a bonus, not a requirement.

In this case it sounds like the extra content doesn't contribute anything useful to the educational experience - in which case, you should let the professor know. (Again, politely and non-combatively.)

I also want to point out that requiring "bundled" course content that goes along with the textbook is closer to assigning a required software package (which, unlike textbooks, you can't buy used or re-sell) than assigning a textbook. I agree with you completely that it's substantially different than being asked to pay for a textbook.

For every class I've ever taken that required specialized (non-free) software, my university installed the software on my laptop for me for free (given that I was registered for the course in question). In most cases, instructors try to use free software or software that comes with a free student license, because they realize that a software purchase is different from a textbook purchase. Or they'll provide the software on lab computers that students can use during set hours.

Imagine if you had to buy a new non-refundable software package for almost every class you were enrolled in, including buying the same software multiple times for a sequence of intro classes on a subject.

Yeah, it's a waste of money, but your professors might not see that unless you point it out.

This is a situation that is in my opinion exploitative and unethical. The majority of the blame lies with the publisher, but some lies with the professor as well. On the professor's part, it's not the kind of behavior that is universally agreed to be unethical, nor is it something that anyone would consider to be extremely unethical (like giving an A in return for a sexual favor).

Here's some background. For decades, publishers have exploited the fact that they could name a price for a college textbook, and it would very little effect on sales, because the adoption decision was being made by the professor, who wasn't the person paying for the book. Over roughly the last 30 years, they have raised the price of textbooks at a rate much too high to be explainable by the combination of inflation and any rise in the costs of production. The skyrocketing price of textbooks has caused many students to find other ways of obtaining the book, and one of these is buying used copies.

Publishers hate the used market and will do anything they can to kill it off. Within about the last 5 years, they've found the magic bullet. They sell the book along with access to a web site, as described in the question. They convince professors to use the online services by appealing to their self-interest. They offer professors an extremely easy and convenient way to obtain an evaluation of their students' work, through the publisher's web site. In many cases, the professor buys in to the system, and then over the following years the price is jacked up more and more. This happened, for example, with Pearson's product Mymathlab, which now costs math students at my school $90 a semester! Professors may not be aware that there are free solutions. E.g., for people who teach math, some good free systems are Myopenmath and Webwork. For physics, there are free systems such as Lon-capa and my own software called Spotter. But the free systems do not have marketing power behind them and may be more work to set up. Therefore professors condemn their students to exploitation through the likes of Mymathlab.

Is this ethical? Wait, is it even legal? How may I fight for our rights as students on this issue?

As a student, you can work through student organizations. Here in California, the student group CalPirg has been working actively on this issue.

As a professor, I try to do my best to inform my colleagues about alternatives to proprietary textbooks and proprietary courseware.

Whether it's legal -- well, I guess that depends on where you live. I think it's legal throughout the US. In Greece, for example, all textbooks are free -- although from what I understand their system is a disaster. Here in California, our former governor Arnold Schwarzenegger tried to get more free and open-source textbooks adopted in K-12, and a state senator named Darrell Steinberg has been trying to do the same at the college level. (Google on SB 1052 and 1053 and California Open Education Resources Council.) Schwarzenegger failed. The jury is out on Steinberg, and I'm not sure his approach is a good idea. If you wanted to get this outlawed in California, Steinberg would be the logical guy to approach.

The problem with trying to deal with this politically is that the current setup appeals strongly to the self-interest of two politically powerful groups: publishers and professors. It's against the self-interest of students, but students don't vote in sufficient numbers to be politically powerful, and they don't have the financial or political resources of the publishers or organizations like the California Teachers Association.

In addition to the, so far, three other fine answers, are these two important points:

(1) Was the compulsory extra course fee announced up front, at the time you signed up or paid for the course? If so, you may have little recourse. On the other hand, if this "extra fee" was sprung upon you after the fact, then this could be an example of trading/bargaining in bad faith and is condemned universally.

(2) Even if the $50 fee for the basic learning kit were deemed acceptable, it appears that the students now have the option of either doing some homework themselves or paying another $40 for someone else (OK, in this case it's a something else) to do it for them. That could be seen, in a small way, as buying an educational credential, and should also be condemned universally.