Professional development has been deemed ineffective for several decades. This ineffectiveness could stem from the one-size-fits-all professional development designs, and the inconsistencies and contradictions pointed out in professional development research (which is used to create these designs). Investigating how subject taught (STEM and non-STEM), Title I status of the school (Title I and non-Title I), and grade level of instruction (elementary, middle and high) could influence teachers' preferences regarding components included in an effective design is a step toward resolving some of these inconsistencies. The research design was an embedded mixed method -- an overall causal-comparative design embedded with interviews. Interviews determined teachers' perceptions of an effective professional development design. The survey investigated preferences for nine components: content knowledge, pedagogical knowledge, active learning, duration, alignment with goals and policies, follow-up, collaboration, support, and resources (tangible and intangible). In the interviews, teachers communicated a need for differentiation based on grade level of instruction, Title I status of the school, and subject taught, with high percentages of agreement with the final questions of the survey. The ordinal logistic regression indicated that subject taught and Title I status of the school did not have a statistically significant effect on the dependent variable. Breaking up participants according to grade level of instruction (elementary versus secondary) had a statistically significant effect on teachers' preferences regarding the components included in an effective professional development design. This indicated that professional development should be differentiated based on elementary and secondary instruction. When the researcher reviewed the components, some showed that the independent variables, Title I status of the school and grade level of instruction had a statistically significant effect. Although the ordinal logistic regression revealed a lack of statistical significance, percent differences indicated that factors such as subject taught, Title I status of the school, and grade level of instruction influenced teachers' preferences regarding specific components in an effective professional development design. These findings illustrate promise that in a larger study, statistical significance might be present. Thus, professional development should be differentiated based on subject taught, Title I status of the school, and grade level of instruction. [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.]