Much research supports the benefits that quality professional development plays in impacting teacher quality. Experiences in professional development can affect a teacher's growth, the application of varied instructional techniques, and increase student learning. When professional development is well-planned, it can provide purpose, collaboration, commitment, and community among educators because there is a positive relationship between student achievement and how recently an experienced teacher participated in a professional development learning experience. But what are the costs associated with low-quality professional development? Just as boredom and lack of meaningful challenge with an ineffective teacher has been shown to negatively impact students with regression in achievement scores over multiple years, educational leaders must consider the impact of unresponsive professional development on teachers and students. Boredom, underachievement, inciting frustration, low morale, or even unprofessionalism in response to not receiving training that is respectful to their learning needs are not consequences that any school leader or educational reformer would want to perpetuate. Students who do not receive adequate challenge may become at-risk for developing underachievement over the course of several years of being in a learning environment that is not an optimal match. For a teacher who has participated in repeated professional development experiences that are not matched to their learning and performance needs, the impacts on career performance and student achievement could be negative. Every educator would want to avoid the mismatch of professional development that could incite frustration with learning and transfer to the classroom. To do so, teachers need learning opportunities for targeted content-based professional development that is differentiated to their readiness level.