If you have a normal calculator (I'm using a CASIO), you need to change your mode to Standard Deviation mode (by pressing you MODE button, then hitting whatever number is associated to SD.
From here you enter the scores one at a time and then press the Memory key (M+). To find the Mean, press SHIFT and 1, followed by the equals (=) sign. To find the standard deviation, press SHIFT and 2, followed by the equals (=) sign.
Note: Only for the CASIO Scientific calculators! (fx-82TL)