In this paper, we study how to support a human tutor who regulates learners' activities, in a situation of mediated tutoring. Our goal is to provide the tutor with information about the effect of his/her interventions. To achieve this, we adopt an indicator-based approach and define the notion of meta-indicator. The distinguishing feature of meta-indicators is that they follow the evolution of the indicators' values. In order to evaluate our proposal, we conducted field experiments in the domain of object-oriented programming. The impact of the information provided by meta-indicators, both on tutor activity and learner activity, was analyzed. The results suggest that the meta-indicators improve the effects of the tutoring interventions and have a positive impact on learners' activities.