You are downloading the Skoolbag AppX file v18.104.22.168 for Windows Phone. Skoolbag is a free and useful Education app: Skoolbag App for schools. Find your school and pin it to your home screen. Be kept up to date with everything that is happening with your school. ... You can now download the offline AppX file to install & try it.
Download Locations for Skoolbag 22.214.171.124 AppX file
Important Notice: Now Due To Unspecified Limitations, You Can Not Use The Offline AppX File To Install It Any More.
To try to install it manually from an SD card, you should choose one of the server location above to get the offline Skoolbag AppX file, move the file to your phone's SD card and then tap 'Install local apps' in the phone's App list.