Does teaching and learning suffer if students and/or teachers are non-native speakers in a programme taught in English? This politically sensitive questions is the topic of research of Folkert de Jong In his PhD dissertation at Groningen University. His study on English as a Medium of Instruction in Higher Education in a cross-national context found a weak correlation between the starting level in English and the number of credits obtained in his group of 137 students.
More importantly, he found no impact of the fact the programme was taught – and studied – with English as a foreign language on the academic performance.
This follows an earlier study showing that working in a foreign language only weakens the mother tongue when students completely forgo using their modern tongue.