Self-report inventories are commonly administered to measure social and emotional learning competencies related to college readiness. If students respond inattentively or dishonestly, validity will suffer. This study applies several methods of detecting insufficient effort responding (IER) to data from ACT® Engage®. Different methods indicated that between 0.8% and 20.3% of respondents exhibited IER, but filtering those students from the data resulted in negligible improvements in criterion-related validity, coefficient alpha, convergent validity, and confirmatory factor analysis model-data fit. Even so, researchers are advised to investigate IER. Analyses affirmed that the IER detection methods effectively flagged suspect item score patterns, so these methods may still be used to flag individual results as potentially invalid.