Many empirical investigations concerning the use of computer algebra systems (CAS) and symbolic calculators (SC) are restricted to a period of only a few weeks. They do not show long-term effects on students understanding. Therefore, a long term project (2003-2012) was started to test the use of symbolic calculators in Bavarian "Gymnasien" (grammar schools) in Germany. The project started with an evaluation in grade 10 (see Weigand, 2008). During the 2006/07 and the following school years the project was implemented in the 11th grade. The content taught was calculus: basic properties of functions, limits, continuity, derivatives, and applications of calculus. The evaluation of the project was intended to give answers to the following questions: How did basic mathematical skills (algebraic transformations, solving equations) change? How did students use the SC? How did they evaluate the use of the new tool? The results show that it takes a long time (one year) to get students acquainted with the technology. Moreover, hopes have not been fulfilled that students of these project classes would improve to a greater degree (especially in abilities which might typically be supported by the use of the SC, e.g. interpreting graphs) than students in the control classes. In addition, a relationship between the mathematical abilities of students and their ability in using the SC in problem-solving processes was made. The results of this study raise questions concerning the adequate way to support and foster the--theoretically quite often emphasised--new possibilities of CAS and SC in the class room. (Contains 1 table and 9 figures.)