large company demanding unpaid labor from employees; possible class action

I work for a large test-prep company teaching classes for high school students. I am paid as an hourly employee.

I took an assignment to proctor an exam for four hours at $10/hr. After accepting the job, I was told I needed to stop by the office to pick up materials, and then stop by the office again afterwards, at a particular time, to drop them off. Now, instead of a four-hour job and a half-hour travel each way, I have to make three trips, for a total of four hours of transit time for four hours work and $40 total. Essentially, the office is demanding that I perform unpaid courier service.

I showed up for work on time and performed the job I was being paid for. However, because I had an unrelated job to do afterwards, I did not drop the materials off at the office until several hours after the office expected to receive them. On the basis of this, all my future proctoring jobs with the company were cancelled.

I am aware that employees are not compensated for commuting; however, I also don't believe you can send them to do unpaid pickup and delivery work. While I still work for the company in other capacities, I lost future work assignments based on my refusal to perform unpaid work on the employer's schedule.

Additionally, the company regularly demands that teachers perform unpaid labor in preparation for classes. They even say this in writing -- they regularly distribute "manuals" that are supposed to be used to update our teaching materials, with a written warning that the manual is not to be taken into the classroom, but that we should instead use the manual to transfer the information to the teaching materials. Isn't that a demand that an hourly employee perform unpaid labor off the clock? Isn't that illegal?

This is a large public company and there are many teachers in my situation.

Thank you for your assistance.