The purpose of this quantitative retrospective causal-comparative study was to determine to what extent the form of professional development (face-to-face or online) or the level of instruction (elementary or high school) has on classroom teaching practices as measured by student learning outcomes. The first research question sought to determine to what extent the form of professional development affects classroom teaching practices as measured by student learning outcomes. The second research questions sought to determine to what extent the level of instruction affects classroom teaching practices as measured by student learning outcomes. The sample was 432 Ohio teachers who participated in the Ohio Performance Assessment Pilot Project. There were 105 teachers who engaged in face-to-face professional development and 327 teachers who engaged in online professional development. There were 216 elementary teachers and 216 high school teachers. An independent samples t-test with a probability level of p = 0.05 was used to determine the differences in student learning outcomes by form of professional development and level of instruction. This study found there is no statistically significant difference between teachers who engaged in face-to-face professional development (M = 0.519) or online (M = 0.467) or teachers who taught elementary (M = 0.524) or high school ( M = 0.493). These findings suggest when the content of professional development is comparable, the form of professional development and the level of instruction have minimal effect on student learning outcomes. [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.]