Gymnasium and IQ
Only a few specialised gymnasia admit their students on the basis of IQ tests. A 1999 study revealed 10th graders attending a normal gymnasium and 10th graders attending a Realschule had higher IQs than 10th graders attending a comprehensive. It also revealed that the difference was greater in 10th grade than it had been in 7th grade. The media reacted to the charge that comprehensive schools are "the place where intelligence atrophies".
he Max Planck Institute for Human Development stated that nobody was "dumbed down" at the comprehensive school and that those attending a comprehensive in 10th grade did no worse on IQ tests than in 7th grade. The institute also stated that the IQ difference between comprehensives on the one hand and gymnasia and Realschulen on the other was greater by 10th grade than in 7th grade because the mean IQ of those at gymnasium and Realschule had risen. The institute did not believe, however, that attending Realschule or gymnasium boosts students' IQ. Instead, they stated that students with lower IQs who attend gymnasium or Realschule might find themselves increasingly unable to keep up and thus may drop out by 10th grade.
Gymnasium and performance on standardised tests
As has been mentioned before, gymnasia and Gesamtschulen in Germany do not administer standardised tests to their students and few students are familiar with those kinds of tests. Yet, scientists sometimes use standardised tests to evaluate schools. 10th graders attending a gymnasium have been shown to outperform 10th graders attending a comprehensive school by one standard deviation on a standardised mathematics test. That equals 2 to 3 years of schooling. Proponents of comprehensive schools have criticised such studies, stating they believe standardised tests to be biased against those attending comprehensive school. They have said comprehensives taught their students "Independence, capacity for team work, creativity, conflict management and broad mindedness" and that those qualities cannot be measured on standardised tests.
Gymnasium and selflessness
According to a disputed study evaluating students' character, based on a standardised test, those attending a Realschule or gymnasium were more likely to be respectful and considerate of other peoples' feelings than those attending a comprehensive school. According to this study, gymnasium students were more likely to be classified as "selfless" than students attending any other kind of school and those attending a comprehensive were more likely to be classified "self-serving" than those attending any other type of school. This study has been widely criticised. It has been claimed that character cannot be measured on standardised tests and that students' answers might not reflect their real behaviour. Charges were raised that questions were worded in academic language thus, students attending a comprehensive may not have understood them properly. It has also been suggested that the answers the students gave may have been influenced by social class, that gymnasium students may have been brought up to think they were selfless, while really they were not. Proponents of comprehensive schools stated gymnasium students were phony and elitist while pretending to be selfless.
Gymnasium and performance on the TOEFL
A study revealed that college-bound students attending a traditional gymnasium did better on the TOEFL than college-bound students attending a comprehensive, but those did better than college-bound students attending an "Aufbaugymnasium", "Technisches Gymnasium" or "Wirtschaftsgymnasium" (the last three schools serve students, who graduated from another school receiving no Abitur and give them the opportunity to earn the Abitur).
| Type of school | Percentage of students earning at least 500 points | Percentage of students earning at least 550 points | Percentage of students earning at least 600 points |
| Traditional gymnasium | 64.7 % | 32.0 % | 8.1 % |
| Comprehensive school | 30.5 % | 11.3 % | 2.2 % |
| Aufbaugymnasium | 18.9% | 5.2 % | .9 % |
| Wirtschaftsgymnasium | 19.7 % | 5.7 % | .4 % |
| Technical gymnasium | 22.3 % | 12.6 % | 1.0% |
Defending comprehensive schools
Proponents of comprehensive schools often hold the opinion that it is unfair to compare gymnasia and Realschulen with comprehensive schools. While gymnasia and Realschulen often handpick their students, comprehensives are open to all.
Proponents of comprehensives also think they lack the most academically promising young people, who have been skimmed off by other schools. They also point out that some comprehensives (such as the "Laborschule Bielefeld" and the "Helene Lange School" in Wiesbaden) ranked among Germany's best schools.