Survey research reveals that a majority of academics believe that research and teaching are positively related. Although correlation does not imply causation, it is clear that many do hold a causal view in which active research is believed to be essential for good teaching. Certainly, anecdotal evidence is consistent with such a view. I was involved recently in a Quality Audit of a New Zealand University in which the research-teaching relationship was explored with a group of undergraduate students. They were quite clear in their view that staff who were active in research were better able to stimulate and maintain interest in their classes.
More formal evidence is less clear.
The authors concluded that although it is inconceivable that an effective teacher in a University could be unaware of recent research, it is not clear that an effective teacher has to participate in the generation of this research. A somewhat different picture emerges, however, when one examines the issue at an institutional level. I recently examined the data on teaching and research quality in UK Universities in which each institution is assigned an average teaching assessment score and an average research score. The correlation between the two is 0.73 indicating that at an institutional level, there is considerable communality between the quality of teaching and the quality of research. The University already has a high proportion of Awards for Excellence in Teaching going to staff who are widely recognised as active in research.