Hi Lisa,
Research on engineering education with these sorts of documented findings is still in its infancy. 
Here are a few more resources I would suggest:
Engineering in Pre-College Settings (2014) Purzer, Strobel, and Cardella (Eds.) 
Schauble, Klopfer, and Raghavan (1991) Students' transition from engineering model to a science model of experimentation 
Klodner J.L, Camp, P.J. et al (2003) Problem-based learning meets case-based reasoning in the middle-school science classroom
Silk, E. M., Schunn, C. D., Cary, M. S. (2009). The impact of an engineering design curriculum on science reasoning in an urban setting.
We also have a compilation of research that my team and other researchers have done on our elementary engineering curriculum. See: http://www.eie.org/sites/default/files/executive_summary_2014.pdf

Hope that helps.
Christine Cunningham

Hi Lisa,

A good place to start may be the book, "Achieving science and technological literacy through engineering design practices." L. Annetta & J. Minogue (Eds.).

Another would be the "Engineering in K-12 Education" report by the National Research Council. Pages 51-55 would be of particular interest to you. There are several studies referenced in those pages that look at achievement of middle school students. The report is available for free download (http://www.nap.edu/catalog/12635/engineering-in-k-12-education-understanding-the-status-and-improving). 

Hope these resources help!