PRINCETON REVIEW has sold assets of its Higher Education Readiness Division, best known for its standardized test prep guides, to Boston-based private equity firm Charlesbank Capital Partners for $33 million. Also included in the sale are all the rights to The Princeton Review name. The soon-to-be-renamed company's press release suggests this transaction was made in the interest of its Penn Foster Division, an online education provider of career-focused degrees and vocational programs.