This study examines the effects of integrated science, technology, and engineering (STE) education on second-, third-, and fourth-grade students' STE content knowledge and aspirations concerning engineering after validation of the measures. During the 2009-2010 school year, 59 elementary school teachers, who attended a week-long engineering teacher professional development (TPD) program, implemented STE integrated lessons in schools in a large, south-central U.S. school district. At the beginning and end of the school year, the Student Knowledge Tests (SKTs) and the Engineering Identity Development Scale (EIDS) were administered to 831 students either in classrooms with the STE integrated lessons (treatment) or without (control). Item and confirmatory factor analyses provided sufficient reliability and validity evidence of the SKTs. Significant differences between treatment and control groups for all three grades on the post-SKTs indicate the impact of STE integration on students' content knowledge. The EIDS showed no significant group differences on the academic subscale, while the engineering career subscale showed that treatment group students scored significantly higher than control group students in all three grades. Those significant changes in the treatment group in knowledge and aspirations are strong evidence for the potential impact of STE integration.