OK, I'm kidding, but here's a little snippet from an education journal.
Mr. Hull said that it's important that rigorous courses live up to their names. For instance, he noted that the College Board reported that student participation in calculus rose 33% for the class of 2013 from 26% fro the class of 2012, yet average math scores for students (on the SAT) dropped to 600 from 607 among the students who took that course. Mr. Hull said that raises a red flag that there may be rigor in title only, not content.Or maybe, just maybe, Mr. Hull, if you increase enrollment you lower the ability level of the average student taking the course, and ergo scores drop.
From my own experience, if you require more advanced math at the high school level, more students who are not ready for advanced math due to ability or motivation take advanced math, and scores drop. Does that make the course less rigorous or the teacher a poorer teacher? No, it clearly doesn't, it dilutes the pool. I enjoy being a teacher but I sometimes wonder at the drivel that passes for education "research" and the suspect thought process that goes into making arguments about education.