This correlation study examines the relationship between participation in online embedded professional development communities and student achievement gains in a College Algebra course taught by high school teachers to high school students for college credit. The participating teachers met weekly through a web-based meeting format using synchronous audio and video. The investigation examines whether a correlation exists between teacher participation in two types of professional development communities and student achievement gains. The two types of Professional Development Communities in this study were: Professional Learning Community (PLC), where teachers were actively engaged in learning instructional strategies with embedded mathematical content, and Professional Support Community (PSC), designed to facilitate support for implementation of instructional strategies. Teacher characteristics were also investigated for correlation with student achievement gains. Teacher characteristics in this study included: teacher activities, teacher certification, teacher years of experience, and teacher contact hours. In addition, the investigation examined whether a correlation existed between student characteristics and student achievement gains. The student characteristics in this study were: Student ACT math score and the number of high school math classes a student completed prior to taking College Algebra. The primary variable was percent of participation in Online Embedded Professional Development in mathematics education. A regression model has shown that there was a significant positive relationship between teacher participation in Online Embedded PLC and student achievement gains. Teacher participation in Online Embedded PSCs did not have a positive relationship with student achievement gains. The study revealed that teacher years of experience had a significant positive relationship with student achievement gains during the Professional Learning Community. The study results indicated that as the amount of instructional time increases, there is a positive relationship to student achievement gains. There was not a significant relationship between student characteristics and student achievement gains. The results of this study indicates that when teachers are actively learning new instructional strategies with new embedded mathematical content in a Professional Learning Community, there is a positive relationship to student achievement gains. [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.]