The "Prima" consists of the Unterprima and Oberprima, the last two years before graduation in a Gymnasium.

Klassenbezeichnungen (class names):
Classes are as a rule counted from 1 to 13; at Gymnasium, they have special names in some federal states
from class 5 upwards:
Sexta (VI)- Quinta (V)- Quarta (IV)-
Untertertia (U III)- Obertertia (O III)-
Untersekunda (U II)- Obersekunda (O II)-
Unterprima (U I)- Oberprima (O I)

http://www.lernen-aus-der-geschichte.de/resmedia/document/do...

senior

Oberstufe (grades 11-13)
At the Gymnasium the old Latin names are still in use: e.g. 11. Klasse=OBERSEKUNDA,
12. Klasse=UNTERPRIMA, 13. Klasse=OBERPRIMA. The students
are between 16 and 20 years of age.

http://www.fulbright.de/togermany/resources/primer.pdf#searc...

In a letter dated 17.03.1932 the Senator responsible for the Secondary School Education Authority informed the Reichsminister des Innern (Home Secretary), in Berlin, that the Talmud Tora Realschule had become a secondary school with sixth form, through the extension of the school with Obersekunda, Unterprima (lower sixth) and Oberprima (upper sixth), and following the sitting of the first Reifeprufung (university entrance examination = A Levels) at Easter 1932 would be acknowledged as an Oberrealschule. Following this the school officially used the title: Tamud Tora Schule (Volks- und Oberrealschule) in its correspondence and documents. It retained this name until April 1937.
http://www1.uni-hamburg.de/rz3a035//1grindelhof.html

This Gymnasium too, like the one in Constance, was a state
school. Here Heidegger would complete the Obersekunda, the Unterprima, and the Oberprima, corresponding to the upper fifth form and the lower and upper sixth forms of the British system. Photographs of Heidegger during each of these three school years have been published in Walter Biemel’s Martin Heidegger.35

http://www.stanford.edu/dept/relstud/faculty/sheehan/pdf/Leh...


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Note added at 24 mins (2006-09-17 15:21:51 GMT)
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• als (veraltetes) Hauptwort "Prima" die oberste Schulklasse eines Gymnasiums (auch unterteilt in die "Unterprima" und "Oberprima", d.h. in die vorletzte und letzte Klasse), vor dem Abitur. (Davor kamen entsprechend die "Sekunda", "Tertia", "Quarta", "Quinta", "Sexta" - vgl. Jahrgangsstufe.)
http://de.wikipedia.org/wiki/Prima