This paper reports how 188 high school students identified as gifted in science were assessed with the Misconceptions-Oriented Standards-Based Assessment Resource for Teachers (MOSART). Students enrolled in a year-long science-centered curriculum where this instrument appeared to be a means of identifying standards-aligned progress, avoiding ceiling effects and reliance on content mastery. This paper discusses two questions: 1. Is the MOSART a valid measure of conceptual understanding in gifted students? and 2. Can the MOSART be used with this population to measure growth in understanding? We present results from the physics and chemistry tests, and consider results from the earth science and astronomy tests. We also discuss refinements to administration procedures and work expanding the subject pool in the coming year.