In 2018, the National Science Foundation supported the sixth in a series of surveys through a grant to Horizon Research, Inc. (HRI). This series of studies has been known as the National Survey of Science and Mathematics Education (NSSME). The 2018 iteration of the study included an emphasis on computer science, particularly at the high school level, which is increasingly prominent in discussions about K-12 STEM education and college and career readiness. The 2018 NSSME+ (the plus symbol reflecting the additional focus) was designed to provide up-to-date information and to identify trends in the areas of teacher background and experience, curriculum and instruction, and the availability and use of instructional resources. This report focuses on trends in mathematics education between 2012 and 2018. The research questions addressed by the study were: (1) To what extent do computer science, mathematics, and science instruction reflect what is known about effective teaching? (2) What are the characteristics of the computer science/mathematics/science teaching force in terms of race, gender, age, content background, beliefs about teaching and learning, and perceptions of preparedness? (3) What are the most commonly used textbooks/programs, and how are they used? (4) What influences teachers' decisions about content and pedagogy? (5) What formal and informal opportunities do computer science/mathematics/science teachers have for ongoing development of their knowledge and skills? and (6) How are resources for computer science/mathematics/science education, including well-prepared teachers and course offerings, distributed among schools in different types of communities and different socioeconomic levels? Complete details of the study--sample design, sampling error considerations, instrument development, data collection, and file preparation and analysis--as well as copies of the instruments are included in the "Report of the 2018 NSSME+" (ED598121). The report is organized into the following major topical areas: mathematics teachers' backgrounds and beliefs; teachers' opportunities for professional development; time spent on mathematics in the elementary grades and mathematics offerings at the secondary level; instructional objectives of mathematics classes and the activities teachers use to achieve these objectives; availability and use of various types of instructional resources; and factors that are likely to affect mathematics instruction, including school-wide programs, practices, and problems.