This article refers to these products:

KidWind Basic Wind Experiment Kit (KW-BWXC)
KidWind Advanced Wind Experiment Kit (KW-AWXC)

Short answer:

You can get by with one class pack, but it will be easier on you and the students if you get a few extra items.

Longer answer:

We recommend that a classroom be set up with three testing stations, with a turbine tower, a ~ 20-inch window fan, and measurement tools at each station. Any more than that and it gets too loud and the wind is too chaotic, unless you have an unusually large space.  We also recommend that each group of students have their own Wind Turbine Hub and blades, which they can continue to modify and use from one day to the next.

One classroom pack (either the Basic or Advanced) includes the materials needed for the three testing stations, and Wind Turbine Hubs, dowels, and blade materials for eight groups.

If you have multiple classes using the KidWind materials, we recommend  purchasing additional hubs so each group of students will have their own hub for the duration of the instructional unit. Additional hubs can be purchased in 10-packs and 3-packs.

You can get by with only enough hubs for each group in the largest class, and have each class use the same hubs with their own blades, but we think it is easier to have the hub and blades stay together.

The classroom pack comes with one Power Output Board. You can use this at a testing station, but we recommend purchasing two additional if you plan to use them for measuring turbine output voltage. A better option is the Go Direct Energy Sensor, of which we recommend purchasing three, one for each testing station.

Three blade pitch protractors are included in the classroom pack, and while these can be easily shared among groups, it is easier if each group has one to use. We recommend purchasing at least five additional blade pitch protractors so that each group will have one at their work area. We also recommend having a set of rulers and scissors for each group to modify their blades. 

The following consumables are included with a classroom pack:

150 dowels (¼ inch diameter)
25 balsa wood sheets (3”x12”)
50 chipboard sheets (3”x12”)
25 chipboard sheets (8.5” x 11”)

You will need additional dowels and blade materials. At a minimum, be prepared for at least 6 turbine blades per group of students, and each blade requires a dowel. We sell precut extra dowels that fit the wind turbine hub. You can purchase ¼ inch dowels and then cut them to the appropriate length. Blade materials can be anything students want to try, that can be attached to the dowels. We also sell chipboard (thin cardboard) and balsa wood for blade materials, as well as balsa wood cut to an airfoil profile. Our Blade Design Consumables pack includes dowels, chipboard, and balsa wood.

Additional information:

What equipment do I need to study wind energy?
What is the best way to attach turbine blades to the dowels?
Which KidWind Kit should I buy?
Can I purchase individual parts from one of the KidWind kits?