The Teachers Know Best research project seeks to encourage innovation in K - 12 education by helping product developers and those who procure resources for teachers better understand teachers' views. The intent of Making Data Work is to drill down to help educators, school leaders, and product developers better understand the challenges teachers face when working with this critical segment of digital instructional tools. More than 4,600 teachers from a nationally representative sample were surveyed about their use of data to drive instruction and the use of these tools. This study focuses on the potential of a specific subset of digital instructional tools: those that help teachers collect and make use of student data to tailor and improve instruction for individual students. The use of data is a crucial component in personalized learning, which ensures that student learning experiences -- what they learn and how, when, and where they learn it -- are tailored to their individual needs, skills, and interests and enable them to take ownership of their learning. Personalized learning is critical to meeting all students where they are, so they are neither bored with assignments that are too easy nor overwhelmed by work that is too hard.