In Bavarian Grade 10 math classes using CAS:

-Competence improved in topics involving work with graphs and switching between representations.
-Algebra skills developed developed to the same level as non-CAS classes.
- Poor and average students improved more than good students.
- Student reaction to the graphing calculator was mixed.

In addition, teachers reported that new teaching methods are possible with the technology, in individual, small and large group work.

A multi-year study is under way of the use of symbolic calculators  – the TI-Voyage 200 – in six 10th grade classes of three grammar schools in Bavaria (Germany).  The study’s goals are to understand: how basic mathematical skills (algebraic transformations, solving equations, working with tables and formulas) changed; how the questions posed in examinations changed if the students were allowed to use a symbolic calculator (with CAS); how the students evaluated the use of the new tool; and how teaching styles and methods changed in the mathematics lessons.

http://www.didaktik.mathematik.uniwuerzburg.de/weigand/projekte.html