Stanford University conducted a multi-year, rigorous analysis of Waldorf education and found significantly higher positive student achievement outcomes on standardized state assessments by Waldorf students, greater engagement and significantly lower disciplinary action and truancy. These results held across the subsets of African American, Latino and socio-economically disadvantaged students. They also accounted for the initial lag owing to the planned Waldorf progression in education.
In another study, scientists highlighted the need to correct the misperception that Waldorf education is somehow less rigorous, because it is more responsive to children at their developmental stage and holistic.
The full article linked here is from the Waldorf School at Moraine Farm in Massachusetts and is a summary of key findings. It also has a link to the study in its entirety.