Just let us know your best guess. We understand that whilst you are promoting the trip in the school there is a time when you will not be sure of the numbers involved. We will send you a pro forma invoice based on your booking form, and then update it if necessary when you start receiving deposits from the students. Please note that our offers are based on a minimum number of students. This number will be made clear in the offer. If you think you may not reach the minimum number then please contact us in case we can find a solution.