Educators have struggled with maintaining student engagement in science, especially as students transition from primary to middle school and upper grades (Vedder-Weiss & Fortus, 2012). A recent push in science education has been the adoption of the Next Generation Science Standards (NGSS), released in 2013, whose development was guided by "A K-12 Framework for Science Education" (NGSS Lead States, 2013). As a result, more educators have been incorporating curricula that require students to ascertain "disciplinary core ideas" using lenses of "cross cutting concepts" while engaged in "science and engineering practices"; the three dimensions of NGSS performance expectations (PE) also known as three-dimensional learning when in practice. Two curricula, mySci (Washington University in St. Louis Institute for School Partnership, 2020) and OpenSciEd (OpenSciEd, 2021), were compared in terms of student academic achievement and attitudes towards science. The research questions were: (1) To what extent is there a difference between achievement in science by eighth grade students experiencing the OpenSciEd curriculum and those experiencing mySci curriculum as measured by end of unit assessment scores? (2) To what extent is the difference between attitudes toward science by eighth grade students experiencing the OpenSciEd curriculum and those experiencing mySci curriculum as measured by My Attitudes Toward Science (MATS) survey (Hillman et al., 2016)? [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.]