Three service stocks are moving up in their overall rating this week, according to the Portfolio Grader database. Every one of these is graded an “A” (“strong buy”) or “B” overall (“buy”).

Graham Holdings Co. (GHC) is progressing from last week’s rating of B (“buy”) as the company improves to an A (“strong buy”) 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. In Portfolio Grader’s specific subcategory of Earnings Momentum, GHC also gets an A. Shares of the stock have been trading at an exceptionally rapid pace, up threefold from the week prior. The stock’s dividend yield is 10.2%. For more information, get Portfolio Grader’s complete analysis of GHC stock.

Cambium Learning Group, Inc. (ABCD) improves from a B to an A rating this week. Cambium Learning Group provides intervention curricula, educational technologies, professional services, and other research-based education solutions in the United States. In the past week, trade volume fell significantly to half the previous rate. For more information, get Portfolio Grader’s complete analysis of ABCD stock.

Liberty Tax, Inc. Class A (TAX) earns an A this week, jumping up from last week’s grade of B. 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 520.2% from the week prior. For more information, get Portfolio Grader’s complete analysis of TAX 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.