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

American Public Education, Inc. (APEI) earns a D this week, moving down from last week’s grade of C. 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) gets weaker ratings this week as last week’s C drops to a D. 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.

The rating of DeVry Education Group Inc. (DV) slips from a C to a D. 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.