Sandra Tietjens studied in Munich, Lille and Cologne and in her thesis, she focused on language integrated strategies in classrooms during the practical semester of student teachers at the University of Cologne. Prior to her work at the Mercator Institute for Literacy and Language Education, she has worked as a mentor for scientific writing, as a team leader in a project conducting assessments of personal potentials of teenagers, and as a teacher of German as a second and foreign language in different institutions.

Since 2020, she has been working as a research assistant in the Department of Language and the Educational System. She is involved in the federal-state projects  Schule macht stark (SchuMaS)  and Startchancen. 
She also is responsible for the research database Lernertexte (FD-LEX). In addition, she teached in the continuing education program German as a Second Language and in the “DaZ” module for students of all teaching qualifications at the University of Cologne. As part of her teaching activities, she also offers further education in the third phase of teacher training. Her thematic focus is on multilingual didactics, language-sensitive teaching and German as a second language.