This mixed methods study aimed to categorize and analyze the frequencies and percentages of complex thinking in the PARCC practices assessments in English Language Arts grade 10 and Geometry. The Hess' Cognitive Rigor Matrix was used for the first part of the study to code each of the PARCC assessment questions in Language Arts grade 10 and Geometry based on pre-existing codes. Deductive category application was utilized to connect the language from Hess' Cognitive Rigor Matrix to the language of the questions in the tests. To ensure reliability we utilized the double-rater read behind method as in other similar studies. In the second part of the study, a quantitative methods approach was implemented to determine the frequencies. Moreover, descriptive statistics was then utilized to describe the differences and similarities of complex thinking that exist in the language of the PARCC practice assessment. In response to the research questions, the data analyzed revealed the following trends from the Language Arts in grade 10 and Geometry PARCC Practice Tests: 1. The questions in the Language Arts PARCC tests in grade 10 were rated at an overall higher percentage for lower-level questions. 2. The questions in the Geometry PARCC tests were rated at an overall higher percentage for lower-level questions. 3. No questions were placed at the most cognitive complex level. This study suggests that more opportunities for developing complex thinking, which is essential to 21st century learning, is implemented through standardized assessments. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]