history
The first A Classes in NZ arrived in 1966, and since then New Zealand has had a proud history of A Class participation. Designer-builders have often been at the forefront of international competition, with Grahame Davey, Murray Philpott, Mike Drummond, Tom Block and Tim Clissold being some names involved in designing and building boats for the NZ fleet. In 2014, Yachting royalty from ETNZ contributed much to the development of the class in its early foiling years when the world champs came to Takapuna.
In 1956, the "A-Division-Catamaran-Class" was orignally founded in England by the former "International Yacht Racing Union" as a free construction class. 60 years on it is going strong and stands proud as one of the oldest and most active catamaran classes in the World. (source)

The A class is still considered the pinnacle of single-handed catamaran sailing, and boasts a lively international scene. 
The A Class box rule:
Min overall boat weight : 75 kg (165lb)
Max overall boat length : 5.49 mtr (18ft)
Max overall boat width : 2.30 mtr  (7ft 6in)
Max sail area incl. mast : 13.94 sq. mtr. (150sq ft)
In modern A Class sailing, there are two avenues for participation

OPEN 

The 'Open' division embraces the full unrestricted A Class rule to develop full-foiling racing machines that can reach 30kt +. Foiling A Class are seen as one pinnacle of single-handed sailing, inviting the world's best sailors to try their hand at taming these technical machines.
Modern A's are both upwind and downwind foiling capable, due to complex foil shapes and trim systems. Basically every aspect of a foiling platform is optimised to increase flight time and flight efficiency. 'Pin-top' sails have had a revival to move power lower to the deck, decreasing heave effects of the tall 9m+ masts. The A class rule was written in such a way to prevent foiling, however workarounds and material technologies have enabled the phenomenon. Most foiling boats now measure within the mm of the strict box rule to maximise horizontal lifting surface. 

classic

The 'Classic' division allows sailors to enjoy the A at its most simple, refined and accessible form. This division, created in 2020, preserves the pre-foiling developments of the class and has proven successful due to its simplicity and affordability. Around 2/3 of New Zealand's fleet are classics.
Classics are by no means a thing of the past. They are still pushing to the edge of foiling capability, and are often more efficient than foiling boats in sub 5kt conditions due to their reduced weight and better power distribution for displacement sailing. In the breeze, classics permit trapezing upwind and downwind due to impressive apparent-wind efficiency. Development is still happening, and because of this much of the class remains in displacement mode while enjoying the 'classic' A class experience of tinkering, racing and developing.