In 1999, Heschong and colleagues collected data from three school districts and 21,000 students to assess whether an increased amount of daylight in elementary-grade classrooms was associated with improved student performance on standardized academic tests [37, 38]. The amount of daylight was predicted from classroom characteristics such as the window area and presence and size of skylights. The data were analyzed using a multivariate statistical model that controlled to the degree possible for the influence of several other factors on student performance. This study found that students in classrooms with more predicted daylight had substantially higher math and reading scores on the academic achievement tests, and the increases in scores were statistically significant. The large magnitude of the increases in scores, sometimes exceeding 20%, was surprising. Consequently, the study received widespread attention. To determine if these findings could be replicated, another study in a different school district was conducted in 2003 . The amount of daylight was measured—by measuring light levels with electric lighting turned on and off. The measured amount of daylight was not related to student performance. However, student performance was higher in classrooms with a better, primarily larger, view to outdoors.
The 2003 classroom study was also supplemented by two office building studies. The first was a study of call center workers . Worker performance was assessed using the time required to handle calls in normal work. This call center study found that more daylight was generally not significantly associated with work performance, except in one analysis for which more daylight was associated with slightly slower handing of calls. Better view to outdoors from the workstation, compared to no view, was associated with a 6% reduction in time to handle calls, but only in one of three analyses of the data. The second office study  used a cognitive function test to assess performance (and also employed visual performance tests which are not discussed in this document). Workers with the best outdoor view at their workstation, compared to no outdoor view, performed 10% better in the cognitive acuity test and 16% better in the memory test. A 10% increase in measured daylight was associated with only a 0.4% improvement in the cognitive acuity performance and did not affect performance in the memory recall test.
In summary, given the small number of studies performed and their inconsistent findings, no firm conclusions can be drawn at this time about the influence of daylight or outdoor view on school or office work performance.