MIAMI (CBSMiami) – Congress has never shied away from getting involved in public education. But a new study from the Sunlight Foundation shows some of the very members of Congress might need to go back to school.

According to the study, Congress now speaks at nearly a full grade lower than it did in 2005. Currently, Congress speaks at about a 10.6 grade level compared to 2005 when Congress spoke at a grade level of 11.5.

The study found that since 2005, Congressional speech among Republicans has dropped more so than for Democrats. Further, the study found that as Republicans became more conservative, the grade level of speech dropped almost three full grade levels.

A similar correlation was found for Democrats who went further to the left of the political center.

Florida Senator Marco Rubio was graded at a ninth grade level of speech, while fellow Florida Senator Bill Nelson’s speech was graded out at between an 11th and 12th grade level.

To see the full list of Congressional scores, click here.

The Sunlight Foundation couldn’t pinpoint the exact cause of the decline, but noted that junior members spoke at a lower grade level than more senior members.

“Among the newest members (those with 1-3 years in their seat), there is a drop off in speech level as we move from the center out to either extreme of the political spectrum, though the pattern is more pronounced on the far right,” the study said in its analysis.

Republican Congressman John Mulvaney of South Carolina was labeled as having the worst speech in Congress, speaking at a grade level of 7.95. The lowest ranking Democrat was John Garamendi out of California, who spoke at a grade level of roughly 8.92.

For a comparison, the U.S. Constitution is at a level of 17.8; the Federalist Papers are at 17.1; Martin Luther King’s “I Have a Dream Speech” was at level 9.4; and the New York and Los Angeles Times were rated at a level of 14.

The study used the Congressional Record and analyzed it with the Flesch-Kinkaid readability tests.