There are two issue regarding Performance. Aircraft are certified in accordance with a performance schedule of which Schedule A is explained above. These schedules will not go away, but the system of examination for them is changing.
Under the older CAA system you were required to take a performance examination that matched the category of aircraft you wished to fly. The CAA Performance examinations were based upon a hyperthetical aeroplane.
Under JAR-FCL there are 3 performance groups A, B and C which are similar to the UK certification groups A, C and E. These are examined as an integral part of the JAR-FCL professional examinations. Instead of taking an additional Performance A examination based on a Hyperthetical aeroplane, the intention is that you will do an examination on the performance of the actual aeroplane that you are going to fly as part of the Aircraft Type Rating Course. This could be considered as a more practical application of performance examinations.