Margaret Miller and co-authors try to answer this question in a new paper in the World Bank Research Observer. The paper does a meta-analysis of 188 studies conducted in Africa, Asia, Latin America, the United States and Europe.

Are there approaches to teaching financial skills or modifying financial behaviors through educational programs, training, or other outreach activities that have reliable, positive results? The objective of this paper is to analyze the evidence of impact for financial literacy and capability interventions through a systematic review of the evidence. The review includes the use of meta analysis, a statistical technique that pools data from different studies to test for significance in the enlarged sample of observations this creates. This paper is different from most previous narrative reviews in that it focuses exclusively on research that analyzes the impact of financial education interventions. Key characteristics of 188 papers are coded to create a rich data set with the characteristics of the interventions, as well as statistical information on the impact of programs on outcome variables such as general savings, retirement savings, and credit performance. This data set is then used for a descriptive analysis of the literature and for empirical tests using meta-analysis.

…. we find that financial education can affect financial outcomes such as savings and improved record keeping, but does less well in preventing negative outcomes such as loan defaults. These results suggest a role for financial education in improving behaviors where individuals have the ability to exert greater control. Arguably, loan default is imposed by external agencies (banks or other financial providers), and hence can only be avoided secondarily or over the long term if financial education leads to more prudent borrowing decisions. Savings and record-keeping, in contrast, are immediate and primary decisions that can be acted upon by targeted consumers.

More on this here.