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”).

This week, JTH Holding, Inc. Class A (TAX) is making solid headway. The company’s rating improves to an A (“strong buy”) from last week’s B (“buy”) rating. JTH Holding provides federal and state tax preparation services and related financial products through retail offices and online in the United States and Canada. In Portfolio Grader’s specific subcategory of Equity, TAX also gets an A. For more information, get Portfolio Grader’s complete analysis of TAX stock.

Cambium Learning Group, Inc. (ABCD) earns an A this week, jumping up from last week’s grade of B. Cambium Learning Group provides intervention curricula, educational technologies, professional services, and other research-based education solutions in the United States. 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 ABCD stock.

The rating of Graham Holdings Co. (GHC) moves up this week, rising from a B to an A. 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 13.5% over the past month, better than the 1.7% decrease the S&P 500 has seen over the same period of time. The stock has a dividend yield of 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.