The purpose of this study was to determine if science teachers showed a change in their ability to design and implement science lessons that integrate twenty-first century science practices as a result of their participation in a subject-specific professional development program. A qualitative design utilizing inductive analysis was used to investigate teachers' ability to design inquiry-oriented lessons and implement them in the classroom. Eight science teachers participated in the study. Findings showed that teachers have benefited from their participation in the program and were able to plan and implement their inquiry-oriented lesson plans and implement them in the classroom. The analysis also showed that teachers were not able to demonstrate their ability in two dimensions of inquiry (asking scientifically oriented questions and designing and carrying out investigations). Finally, several suggestions were presented to modify the program's training materials to focus more on these two dimensions of inquiry.