Complex sentence: Much of the research on the effects of service-learning is focused on students and what they learn through their service to the community; fewer studies have been conducted on the impact of service-learning on the communities where the students serve.
Split into simpler sentences: Much of the research on the effects of service-learning is focused on students and what they learn through their service to the community. Fewer studies have been conducted on the impact of service-learning on the communities where the students serve.