Clever - syncing between education applications for K-12 schools
Freeplane - Freeplane is a powerful and free software for building mind maps.
PowerSchool - PowerSchool provides a K-12 education technology platform for operations, classroom, student growth, and family engagement.
Linked Ideas - A macOS/iOS apps to treat ideas as links of concepts.
Claroline - Claroline is a collaborative eLearning and eWorking platform.
OmniOutliner - OmniOutliner is a writing app for collecting information, outlining ideas, adding structure to any sort of writing.