From the Super Mario Wiki
The Composition Court is a tennis court from the Game Boy Color game Mario Tennis and Game Boy Advance game Mario Tennis: Power Tour. This court is where the varsity-ranked players play. After Alex, Nina, Clay and Ace play here, they move up to play at the Island Open. It is a green, outdoor (indoor in Mario Tennis: Power Tour) court with a surrounding miniature, white fence that runs along a yellow floor. Also, there are windows facing the court in Mario Tennis: Power Tour.
Mario Tennis (Game Boy Color)
The Composition Court makes it debut in Mario Tennis as the court used by the varsity ranked players. It is only played on once in the story mode, but can be chosen from the exhibition mode at any time. It has the fastest ball speed with a normal bounce.
Mario Tennis: Power Tour
In Mario Tennis: Power Tour, when players are on this court, it is mentioned that the tennis ball travels faster than it does on any other court. The ball's bounce height, however, is normal.