This week, three service stocks are improving their overall ratings on Portfolio Grader. Each of these stocks is rated an “A” (“strong buy”) or “B” overall (“buy”).

Cambium Learning Group, Inc. (ABCD) is progressing from last week’s rating of B (“buy”) as the company improves to an A (“strong buy”) this week. Cambium Learning Group provides intervention curricula, educational technologies, professional services, and other research-based education solutions in the United States. In Portfolio Grader’s specific subcategory of Earnings Momentum, ABCD also gets an A. For more information, get Portfolio Grader’s complete analysis of ABCD stock.

JTH Holding, Inc. Class A (TAX) shows solid improvement this week. The company’s rating rises from a B to an A. JTH Holding provides federal and state tax preparation services and related financial products through retail offices and online in the United States and Canada. Shares of the stock have been trading at an exceptionally rapid pace, up threefold from the week prior. For more information, get Portfolio Grader’s complete analysis of TAX stock.

Graham Holdings Co. (GHC) boosts its rating from a B to an A this week. Graham Holdings is a diversified education and media company whose principal operations include educational services, newspaper print and online publishing, television broadcasting and cable television systems. The stock price has risen 9.1% over the past month, better than the 1.7% decrease the S&P 500 has seen over the same period of time. The stock’s dividend yield is 10.2%. For more information, get Portfolio Grader’s complete analysis of GHC 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.