BASI or the British Association of Snowsport Instructors is one of only 4 worldwide governing bodies (out of about 15) that actually adhere strictly to the teaching and riding standards laid down by the worldwide governing body known as the ISIA. That is why they are one of the most respected organisations in snowsports. That is also why the qualification is accepted worldwide. Its not easy and not to be taken lightly. Other entry requirements are detailed here.