Not really true, at least at my university, and I think at most of the good ones. The syllabus is considered to be a contract between the student and the professor. If a professor tries to spring extra assignments not stated on the syllabus, or grade an assignment based on anything other than academic quality, the student can initiate a grievance procedure and will probably win.
Notice I didn't say there wasn't a guide as to what is expected of the students by the professor, I said there was zero expectation of common practice and grading policy. In short, each professor can pretty much dictate what makes up a students grade. If they want the final to count for 75%, homework to count for 5%, and class attendance to weigh in at 20% so be it. If the next professor wants homework to account for 75%, the final 5%, and bringing a pen, paper, and text book to class each day to account for 20%, that's fine too. In short, no reasonable standardization of expectations.
