The key findings can be summarized as follows: No differences could be identified between Abitur grades of G8 and G9 students and none or only minor differences regarding competencies in mathematics, physics, and biology were shown. However, stress levels were perceived to be higher and the health and well-being of school students who took the Abitur exam after eight years of Gymnasium was found to be not as good. A striking result was the significantly better performance of G9 students within the competence domain of English. However, this result might not necessarily be attributed to the G8 reform, but could be a temporary effect of adjusting the foreign-language concept introduced in the Federal State of Baden-Wuerttemberg, according to the study. Due to these findings, the authors recommend to end any further debate about G8 and G9. 

The data of the study were collected as part of the National Educational Panel Study (NEPS). In total, data of approximately 5,000 secondary-school students in Baden Wuerttemberg from 48 Gymnasien were available; students were interviewed at the end of their school career after the written Abitur exams. The graduation classes of 2011 (G9), 2012 (dual class of first G8 and last G9 year) as well as the first pure G8 class of 2013 were included in the study.

 More detailed information on the study is available here (German only).