The Graduate Record Examination, or GRE, is the standardized test required for admissions to many graduate school programs at U.S. universities. Educational Testing Service, or ETS, administers this examination at testing centers around the world. The general test measures graduate students' verbal reasoning, quantitative reasoning, analytical writing and critical thinking skills. The GRE also offers subject area exams in courses such as literature, biology and psychology. ETS and educational companies provide preparatory courses for test takers.

Educational Testing Service

Educational Testing Service, or ETS, creates the GRE and scores tests given to students from around the world. In addition to administering the test, ETS conducts educational research which, at times, leads them to make revisions to the examination. The ETS website has an online store that sells updated versions of test preparatory workbooks for the general examination. Select workbooks provide CD-ROMs with actual tests, sample essays and test-taking strategies. Once students register for the GRE, they receive sample workbooks to practice.

Kaplan Test Prep

Kaplan Test Prep offers test preparation courses for students entering undergraduate and graduate programs, including GRE courses. It has an array of programs catered to students who want to study alone, online or at testing centers. Students can enroll in online test preparatory courses, paying for the course in installments. The Kaplan website features an online registration form for online students. The website also provides information about test-taking centers where students can get one-on-one tutoring. Test takers can purchase workbooks on Kaplan's website or at bookstores like Barnes & Noble. Test centers also give free paper sample tests.

The Princeton Review

The Princeton Review provides resources for students, parents and educators, as well as educational and career materials. Its Test Preparation Division prepares students as they progress in their quest for higher education. Test preparation material includes test prep courses, tutoring, online materials and books. Test centers offer one-on-one and small group tutoring. Classroom GRE courses divide students according to their shared strengths and weaknesses. Potential test takers can study at their own pace via online courses or workbooks available at bookstores. Test centers also offer free GRE test taking strategy sessions.

PowerScore Test Preparation

PowerScore Test Preparation provides test-taking materials for students preparing for GRE, LSAT, SAT and GMAT exams. The company offers one-on-one personal tutoring, telephone tutoring and GRADadmissions consulting. Personal tutoring sessions take place at testing centers across the United States. PowerScore makes telephone tutoring available to students around the world for an hourly fee. GRADadmissions consulting helps students with their graduate school application, including telling them what GRE scores are needed for graduate programs at different universities. PowerScore also offers 16-hour lectures that take place over two weekends. The 16-hour course has an online student center, test-taking techniques and email assistance.