This week, four 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 showing good progress as the company’s rating jumps from a B (“buy”) last week to an A (“strong buy”). 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) 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. For more information, get Portfolio Grader’s complete analysis of ABCD stock.

Apollo Education Group, Inc. Class A (APOL) is bumping up its rating from a C (“hold”) to a B (“buy”) this week. Apollo is a private-education provider at the undergraduate, graduate, and doctoral levels. For more information, get Portfolio Grader’s complete analysis of APOL stock.

Collectors Universe, Inc. (CLCT) is seeing ratings go up from a B last week to an A this week. Collectors Universe provides third-party authentication, grading, and related services for rare and collectible items. For more information, get Portfolio Grader’s complete analysis of CLCT 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.