The winners of each heat will go through to finals on May 3 and May 4.
Here are some of the best pictures from the heats, captured by photographer Vernon Nash.
. Arms in the air
The Federation of Trosnant Schools Picture: Vernon Nash Photo: Vernon Nash
. Striking a pose
Priory School Photo: Vernon Nash
. Rubik's Cube
Priory School Photo: Vernon Nash
. Colours
Portsmouth Grammar School Photo: Vernon Nash
. Red Riding Hood
The Portsmouth Academy Photo: Vernon Nash
. Woodland
The Portsmouth Academy Photo: Vernon Nash
. Scary
Baycroft School Photo: Vernon Nash
. Suffragettes
Wimborne Primary School Photo: Vernon Nash
. Masked ball
Chichester College Photo: Vernon Nash
. Solo turn
Chichester College Photo: Vernon Nash
. Silhouette
Baycroft School Photo: Vernon Nash
. Dreamcatcher
Wicor Primary School Photo: Vernon Nash
. Routine
The Federation of Trosnant Schools Photo: Vernon Nash
1. Striking a pose
Priory School Photo: Vernon Nash
2. Rubik's Cube
Priory School Photo: Vernon Nash
3. Colours
Portsmouth Grammar School Photo: Vernon Nash
4. Red Riding Hood
The Portsmouth Academy Photo: Vernon Nash