Learning Gains from Teaching with Graphing Calculators
Learning Gains
Conclusion:Teaching with graphing calculators using the techniques identified as successful has been shown to yield average learning gains in the range of 14% to 50%
Virginia Commonwealth University A metaanalysis of 54 highquality studies found higher learning gains due to graphing calculator use in 4 types of learning outcomes for math. Average effect sizes were:
Empirical Education, Inc. A metaanalysis of 6 highquality studies showed an (effect size) due to graphing calculator use of .85. Reference: (Khoju, Jaciw et al. 2005) 
Conclusion:Use of graphing calculators in grades 68 to teach Algebra and for testing is proven effective. Use of graphing calculators for teaching Number and Operations is a promising practice for grades 35, and an emerging practice for grades 912. Use of graphing calculators is a promising practice in grades 912 for teaching algebra, geometry, data analysis and probability.
Center for Implementing Technology in Education (CITEd)
Evidence is emerging, but not yet strong, for teaching Number and Operations in grades 912 with graphing calculators. (See primary sources for definitions of strength of terms.) Reference: (Helsel, Hitchcock et al. 2006) Reference: Center for Implementing Technology in Education (CITEd) 
Conclusion:Teaching with graphing calculators is shown to result in student performance gains
Technical University of Darmstadt, Germany
Reference: (Bruder 2008)

Learning Outcomes
Conclusion:Students using graphing technology have demonstrated better understanding of functions and variables, and performed better in solving algebra problems in applied contexts and interpreting graphs.
Virginia Commonwealth University Handheld graphing technology can be an important factor in helping students develop a better understanding of mathematical concepts, score higher on performance measures, and achieve a higher level of problem solving skills. SRI International Students who have been taught effectively with graphing calculators:

Conclusion:Technology that supports multiple representations is shown to increase students' use of visualization in problem solving and gains in understanding.
University of York A UK review of 14 studies of multiple representations found that gains in understanding and visualization can result from multiple representations, when:
Lower attaining students preferred working with tables, and had trouble moving between symbolic, tabular and graphical forms, depending on the nature of the task assigned. 
Conclusion:Effective teaching with graphing calculators in developmental math has been reported to increase student success and greater student retention.
SRI International 
Conclusion:Appropriate use of graphing calculators is shown to provide all students at various levels greater access to complex mathematical concepts.
SRI International 