Despite the importance of mathematical understanding for academic and occupational success, students in the United States are not meeting necessary levels of mathematics achievement. Multi-tiered systems of support (MTSS) provide a framework for schools to allocate resources to best support students. Universal screening, a key element of MTSS, employs brief assessments of critical academic skills to identify at-risk students. Despite advances in the screening for reading risk, research in mathematics screening is lacking. Current early numeracy screeners target number sense with mixed results. The mental number line is a potential construct for developing more advanced screening measures. The mental number line is a key developmental construct around which students organize their thinking and draw upon when working with elementary mathematics topics. The current study will explore the promise of using a number line assessment as part of a mathematics screening battery to identify students at risk. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]