The grades of three Life Science stocks are better this week, according to the Portfolio Grader database. Every one of these stocks has an “A” (“strong buy”) or “B” overall (“buy”) rating.

This week, PAREXEL International (NASDAQ:PRXL) is making solid headway. The company’s rating improves to an A (“strong buy”) from last week’s B (“buy”) rating. Parexel International is a contract research and product launch organization. In Portfolio Grader’s specific subcategories of Earnings Growth, Earnings Momentum, Margin Growth, and Sales Growth, PRXL also gets A’s. For more information, get Portfolio Grader’s complete analysis of PRXL stock.

Waters Corp. (NYSE:WAT) is bettering its rating of C (“hold”) from last week to a B (“buy”) this week. Waters is an analytical instrument manufacturer that designs, manufactures, sells and services liquid chromatography, ultra performance liquid chromatography, mass spectrometry instrument systems, and support products. For more information, get Portfolio Grader’s complete analysis of WAT stock.

Covance (NYSE:CVD) boosts its rating from a B to an A this week. Covance is a drug development services company providing a range of early-stage and late-stage product development services to the pharmaceutical, biotechnology, and medical device industries. The stock price has risen 7.5% over the past month, better than the 3% increase the S&P 500 has seen over the same period of time. For more information, get Portfolio Grader’s complete analysis of CVD 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.