Some schools aren't able to save to or open files from their server on the iPad. One of my teachers takes a lot of photos and stores them on her laptop, she can't use Photostream as all her photos would end up on other classes iPads as they are all synced to one master computer.
Therefore Dropbox is a great option. Download and install Dropbox on your computer...
...and then download the app from the App Store
Free for iPad; Free for iPhone/iPod Touch)
3 Gig is free
Stores all types of files
Downloads an application to your computer that will appear as a main folder in your hardrive
It is good practice to look at the size of your photos before you upload to Dropbox or Box and compress them if they are larger than 500kbs. Ideal size is between 100-500kbs.
Open the app on your iPad or iPod Touch. Look for the photos, tap on them.
Click on the Share button and select Save Photo, the photo will appear in the Photo Library.