All these great, cheaper devices serve up content fabulously. But in the early days, creating content is where they lacked. That started to change, and we are starting to see great examples of video creation, images, and a great use, mindmaps or brainstorm maps. You can find some pretty good ones on Android, and I will just give you a brief review of a couple.
Mindomo (https://play.google.com/store/apps/details?id=air.com.EXswap.Mindomo) definitely would be my first pick. Free, and pretty powerful. Often, the free apps come limited. A certain number of things created or not all the features. Mindomo breaks that, as you get unlimited maps to share and edit, and then export. You can work offline, then sync your maps. You can collaborate in real time. Definitely the one to check out first!
NotesMappr (https://play.google.com/store/apps/details?id=com.quesucede.notesmappr&feature=also_installed#?t=W251bGwsMSwxLDEwNCwiY29tLnF1ZXN1Y2VkZS5ub3Rlc21hcHByIl0.) is a little different, but think of it as Evernote meets Wikipedia. You can take an infinite number of notes and link them in any way. It is not graphic, but as they say, the ‘textual equivalent of mind maps.’ Very powerful to bring in other resources.
MindBoard Lite (https://play.google.com/store/apps/details?id=jp.osima.android.mindboardlite.free&feature=also_installed#?t=W251bGwsMSwxLDEwNCwianAub3NpbWEuYW5kcm9pZC5taW5kYm9hcmRsaXRlLmZyZWUiXQ..) is obviously the only one of my reviews to come with a paid option. So yes, it does come with limitations, but for a classroom, I think the Lite version would do just fine. You create mindmaps using your finger–yup, just draw. You can easily move things around and export a completed map to the Gallery. So you can only save 10 at a time in the Lite version, or unlimited with the $4.99 full app. Pricey for a 1:1 program, but maybe if you just have a few devices in your classroom, it could work.