During the Cultivating Diverse Talent in STEM (CDTIS) Project, a team of scientists, teachers, and a researcher developed a performance-based assessment of high school students' creative problem-solving skills and ability to apply physical science principles in practical ways. It was one of six measures to identify exceptionally talented students. Students identified using conventional methods (M1), with an average grade point average (GPA) of 3.93, had an average rating of 2.95 on a 5-point scale on the mechanical-technical assessment. The M2 students, who were from schools with high percentages of Hispanic, American Indian, and low socioeconomic status (SES) students, had an average GPA of 3.07 and an average rating of 3.27, demonstrating that this assessment can be an important way to change the cultural and economic balance of students identified as exceptionally talented in Science, Technology, Engineering, and Mathematics (STEM). Other researchers are encouraged to examine the validity of the mechanical-technical assessment to identify exceptionally talented students in different groups.