Could anyone tell me how high the leg should be lifted?

Could anyone tell me how high the leg should be lifted for an arabesque balance?

it depends at what level you are teaching but desirebly it should be at least horizontal or higher. this can be quite hard at low levels or with bad flexibilty so just ask them to lift as high as they can but you must make sure they keep there chest up as high as possible to the back should be arched. when i teach an arabesque i ask them to point 1 leg behind and spot at something still on the wall, then to lift there back leg as high as they can without moving the top half of the body (the leg wont go very high) then they should lean foward keeping the chest up (arched back) and continue lifting the leg as high as possible.