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

This week, Graham Holdings Co. (GHC) is showing good progress as the company’s rating jumps from a B (“buy”) last week to an A (“strong buy”). 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. The stock’s dividend yield is 10.2%. For more information, get Portfolio Grader’s complete analysis of GHC stock.

This is a strong week for JTH Holding, Inc. Class A (TAX). The company’s rating climbs to A from the previous week’s 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. For more information, get Portfolio Grader’s complete analysis of TAX stock.

Cambium Learning Group, Inc. (ABCD) boosts its rating from a B to an A 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.

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.