No matter what the mathematics class, infusing reasoning and sense making into the daily mathematical experience of all high school students is crucial. ""All high school students"" includes low-performing students; gifted students; students of different racial, sociolinguistic and socioeconomic status; students with disabilites and students who are mathematically talented. The writers of this volume hope to further the dialogue about how to create for all students empowering mathematical experiences that incorporate reasoning and sense making.