Free reading comprehension tests can be found on MrNussbaum.com, EnglishTestStore.net, MajorTests.com/SAT and GraduateShotLine.com/TOEFL.html. These range from reading comprehension tests for children to ESL tests to SAT preparation tests.
MrNussbaum.com offers many reading comprehension tests for children from second grade to fifth grade. Each test is a two-page printable PDF. On the first page is a text, and on the second page are multiple choice questions about the text. Topics range from animals to sports teams, but most of the texts are about American history or politics. Answer sheets are also available on the site.
EnglishTestStore.com offers tests ranging from elementary to advanced. The tests are timed and questions are asked one at a time. Answers are checked immediately upon hitting the Submit button.
PearsonLongMan.com offers free practice tests intended for teachers to give to a class. Users can't check answers online. The tests range from the first grade to the eighth grade. Each test has two texts, multiple choice questions and sometimes short answer questions.
GraduateShotLine.com offers practice tests for the Test of English as a Foreign Language, an English as a Second Language test required by many universities in the United States and Canada to prove international students' English proficiency. The reading comprehension tests on the site have 10 multiple choice questions; all 10 questions are scored together upon clicking the Score button.
MajorTests.com offers free SAT reading comprehension tests. Ten of its tests include a long text and seven multiple choice questions, which are scored in total upon hitting Submit. The remaining four SAT reading comprehension tests on the site include three short paragraphs with only two to four questions each.