The main purpose of a screening instrument is to identify students whose performance on the measure warrants further investigation. Because screening does not directly result in diagnosis, it is better for a screening instrument to err on the side of false positives (students identified as at risk, who through more intense assessment are found to have been misidentified) than on the side of false negatives (students not identified through screening who later turn out to be at risk). Therefore, a wider net with which to capture potentially at-risk students can be cast with screening measures. A potential drawback of having more false positives is the added expense of the additional testing and the provisions of services to more students, while a drawback of having more false negatives is that those students miss the opportunity to benefit from early intervention services. Ultimately, however, a school will want to find a measure that reaches an acceptable balance of efficiency and accuracy. To do this, schools will need to maintain data on how well the measure identifies students as at risk (e.g., track the number of false positives and false negatives). Such fine-tuning can help save resources.