**A. Appendix A: definitions and operationalization for gateway classes**

#### **A.1 Definitions (Conceptualization)**

*Gateway Classes* are lower-division, required courses characterized by high enrollment, high failure and withdrawal rates that serve as a significant barrier to further study, degree completion, and ultimately, the professions [2].

*Gateway Classes at Trinity*: The time period under analysis is between Fall 2015 and Spring 2020. For a course to meet the requirement of a gateway class, at least 15 percent of the students (on average) had to receive a D/F/W. The classes under analysis are in the areas of Math (Calculus 1 and Calculus 2), Life Sciences (Integrative Biology 1, General Chemistry, Introduction to Chemistry, and Organic Chemistry),

the Physical Sciences (Introduction to Magnetics, Intro to Elec, Magn, and Waves), Computer Sciences (Principles of Computer Science 1), Engineering (Mechanics 1), Business (Fundamentals of Accounting 1), and the Social Sciences (Principles of Microeconomics 1). The total enrollment of students taking these classes during the time period under analysis is 9070.

*Multiple Gateway Classes* are when a student takes more than one gateway course in the same semester.

*First-Generation Student (FG)*: The first student in the family that will graduate from a 4-year college.

*PELL Eligible Student (PE)*: The Federal Pell Grant is usually awarded to undergraduates who have a high degree of unmet financial need. Students whose families have a total income of up to \$50,000 may be *eligible* for the need-based funding, though most Pell grant money goes to students with a total family income below \$20,000.

*Quantitative and Reasoning Skills (QRS) Director*: As a result of Trinity's Quality Enhancement Plan titled *Starting Strong*, the university hired a QRS Director. The Director is tasked with supporting "STEM faculty efforts to assist students facing quantitative reasoning challenges" (*Starting Strong*, 2018, p. 35). Additionally, the QRS Director implements software support, oversees mathematics placement, and tutorial software (i.e., ALEKS), provides meaningful interventions with students struggling in STEM-related courses, assists in offering the Summer Bridge Summer STEM course, teaches Calculus 1 (Math 1311), and oversees peer tutors, among other activities (Ibid, pp 35–36).
