Technically, the father hasn't yet become a tenured high school teacher, so if technical accuracy is important, he's a non-tenured high school teacher.

Kultur: A Studienreferendar has passed the first Staatsexamen and must teach at least two years and pass a second exam before becoming a Studienassessor, and only later a (tenured) Studienrat.
http://german.about.com/library/blvoc_educ2.htm

24Teachers in German high schools, for example, follow the career trajectory "Studienassessor,"
"Studienrat," and "Oberstudienrat." The rate of transition is usually three to five years. This pattern is the
common pattern for all civil servants in West Germany.
http://library.mpib-berlin.mpg.de/dl/Studien/Studien_049/pdf...

Studienassessor (probationary teacher) and Studienrat (tenured graduate secondary teacher) for physics and mathematics at a variety of secondary schools (stages I and II) in Bremen.

http://www.uni-essen.de/fischer/dox/11.1151.HydVv.H.En.php

Studienrat – Johanna Timm
professional title of a public servant, namely of a teacher at a secondary school who has served in his/her profession for several years after the second state examination.
There are various steps involved before you can call yourself a Studienrat- Studienreferendar, -assessor. After you have served as a Studienrat for some time, you might be promoted to Studiendirektor.
http://www.proz.com/kudoz/15686