[Garrett.d.w]

The above posts give good answers on the paperwork required for international travel.
A few more things just for general travel.

Know who people are and where you are going!
In my personal experience traveling it is important that everyone can answer the basic travel related questions quickly and uniformly (ie, get the same or similar answer from each kid). Also, make sure that everybody knows each others legal name. It is common for officers to ask a random passenger to give the name of the driver or some other person in the car.

Look Organized
People should wear team shirts or some form of uniform apparel. All student information should be in a binder and folder, etc. The idea is that when you roll up to the crossing, you can supply all of the correct information quickly and efficiently and look official. Because you look like you know what you are doing they will trust your answers more and spend less time on you (and find fewer things that are wrong).

Pack Neatly
As mentioned in a post above, keep a list of every tool you pack and where it is. Also, pack things so that they are easy to remove and easily displayed if they want an inspection.