My research involves the Successful Start: Cognitively Guided Instruction (CGI) project which provides mathematics professional development to Hillsborough County teachers serving students in grades VPK to 3rd grade. The CGI program that will be provided to teachers during the Successful Start: Cognitively Guided Instruction project is based on an Evidence-Based CGI program that meets the What Works Clearinghouse standards for moderate evidence of effectiveness. This is particularly important because CGI is one of very few mathematics teacher professional development programs that have this level of proven evidence of effectiveness.