Great work on this resource
Sorry for not getting back to you earlier. (I didn't turn the deforestation page to "watch" so I didn't get a notice of your reply.) I saw a link to your project and thought I'd check in to see how it's coming along. Wow, you and your team have created a wonderful resource. Kudos to you all!
So about categories. Looks like you have successfully created a category for all of the pages in this resource. The next step is to make that category a sub-category of something larger. I think your resource should be categorised in Category:OERNZ_Primary_school. Just as you added the code [[Category:Deforestation_for_primary_students]] to your resource pages, you will add [[Category:OERNZ_Primary_school]] to your Category:Deforestation_for_primary_students page. You'll notice that Category:OERNZ_Primary_school is a subcategory of Category:OERNZ_School.
You can create more categories as needed and hook them together. For example, if the deforestation resource is classified into particular subject areas (or a combined subject area), you could put the deforestation category into those as well. And hook them together with the other OERNZ categories in the same way.
I have to hurry out now, but I'll pop back later to take a closer look. Alison