You or your children may want to move up or down a level because:
you/they are not sure you have selected the right level upon checkout
you/they progress quicker than you thought you would
Of course this is possible to move up or down a group when you arrive in resort. Your ski instructor will assess your ability level and how quickly you are progressing. If they feel that you’re doing well, or have been put into the wrong group, they will move you accordingly.