First of all, I seem to recall my HS yearbooks running somewhere over $35. In addition, to that you also had to order them a couple months ahead of publication. The order forms (well, packets) were handed out in 2nd period (which was our version of homeroom) It was not a random thing.
As far as I can tell, this is the norm, as the companies that do the publishing set up how it works, rather than the schools themselves.
If the special ed program had always been included in the yearbooks and the yearbooks were sold via forms handed out from facility to students, well, than Mom has a big point and the school is the tool.