This paper reports on a large-scale experiment that introduced and evaluated an intelligent tutoring system, PAT (PUMP Algebra Tutor), in an urban high school setting. The success of the project was attributed to a client-centered design approach that integrated the expertise of mathematics educators and cognitive psychologists. The Pittsburgh Urban Mathematics Project (PUMP) developed an algebra curriculum focused on real-world problem-solving and computational tools. PAT, a cognitive tutor, supports this curriculum and has been integrated into 9th-grade algebra classes in three Pittsburgh schools. In the 1993-94 school year, students using PAT outperformed those in comparison classes by 15% on standardized tests and 100% on tests targeting PUMP objectives. The study provides evidence that intelligent tutoring systems can be effectively scaled up and implemented in urban high schools, enhancing both technical and pedagogical aspects.This paper reports on a large-scale experiment that introduced and evaluated an intelligent tutoring system, PAT (PUMP Algebra Tutor), in an urban high school setting. The success of the project was attributed to a client-centered design approach that integrated the expertise of mathematics educators and cognitive psychologists. The Pittsburgh Urban Mathematics Project (PUMP) developed an algebra curriculum focused on real-world problem-solving and computational tools. PAT, a cognitive tutor, supports this curriculum and has been integrated into 9th-grade algebra classes in three Pittsburgh schools. In the 1993-94 school year, students using PAT outperformed those in comparison classes by 15% on standardized tests and 100% on tests targeting PUMP objectives. The study provides evidence that intelligent tutoring systems can be effectively scaled up and implemented in urban high schools, enhancing both technical and pedagogical aspects.