There has been a lot of media attention to a Sunlight Foundation report that says, "Today’s Congress speaks at about a 10.6 grade level, down from 11.5 in 2005." The trouble is, the researchers based their analyses on member statements in the Congressional Record but they failed to distinguish among types of statements. The best test of communication levels would be unfiltered member speeches, but there is little of that in the Record, though perhaps a little more in committee transcripts. That's because staff have the opportunity to "clean up the record" before publication. I've done it for four Senators, all very articulate and bright, but still prone to the occasional garbled or run-on sentence in the heat of debate. The staff's job is to make the prose sing.
Another difference is that a lot of material in the Record is staff-written statements. These reflect the skill, education level, and purposes of the staff much more than the member. Some statements are written for media releases and are punchy and quotable, and thus probably at a lower education level. Others are erudite and complex, reflecting the subject matter and the purposes of information and persuasion.
Given these different authors and goals of statements, it's highly misleading to conclude anything about the education level of congressional speech.