Jeremy Scott, of The Royal Society of Edinburgh, just released version 2 of his middle/high school curriculum on mobile app development that features MIT App Inventor. The new resources include a tutor pack, learner pack, screencasts, apps, and media files, all downloadable and free to use.
This is a great update to Jeremys original I Love My Smartphone curriculum, which used version 1 of App Inventor. The new version has been updated to use App Inventor 2. Please check it out! https://www.rse.org.uk/schools/teachers/resources/
Please note, you will have to scroll down the page to Computing Science Resources and look for I Love My Smartphone.