The overall ratings of three service stocks are down on Portfolio Grader this week. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

The rating of American Public Education, Inc. (APEI) slips from a C to a D. American Public Education provides online postsecondary education focusing on the needs of the military and public service communities. As of Sept. 4, 2015, 10.2% of outstanding American Public Education, Inc. shares were held short. For more information, get Portfolio Grader’s complete analysis of APEI stock.

Career Education Corporation (CECO) earns a D this week, falling from last week’s grade of C. Career Education provides on-ground private, for-profit, postsecondary education in the United States, in addition to having a presence in online education. The stock gets F’s in Equity, Cash Flow and Sales Growth. To get an in-depth look at CECO, get Portfolio Grader’s complete analysis of CECO stock.

DeVry Education Group Inc.’s (DV) rating weakens this week, dropping to a D versus last week’s C. DeVry provides educational services worldwide and operates various institutions of higher education. As of Sept. 4, 2015, 16.5% of outstanding DeVry Education Group Inc. shares were held short. For more information, get Portfolio Grader’s complete analysis of DV stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.