ArcGIS Online is an online, collaborative web GIS platform to create, and share maps, scenes, apps, layers, analytics, and data. Features include access to the Living Atlas of the World, apps, and Esri’s secure cloud. ArcGIS online is used by GIS professionals, not for profits, geography enthusiasts and most importantly, by educators in classrooms around the world. More information: https://doc.arcgis.com/en/arcgis-online/reference/what-is-agol.htm
Through The ConnectEd Initiative, Esri offers free online mapping tools and activities for schools. It's easy for teachers to sign up for a free ArcGIS Online Organization account. Just visit ConnectEd Esri and scroll to the bottom of the page http://www.esri.com/connected !
Included in the ArcGIS Online platform are Story Maps, also known as apps. There are many Apps to choose from depending on the story you want to tell. For example swipe maps, may be used to compare and contrast maps; story map tours work well for showing the tourist destinations in a city and a map journal is perfect when in-depth narrative is required. A great example of an Illinois based story map, using the map journal format is Forests of Illinois 2015.
To learn more about making Story Maps visit Story Maps Tutorial.
Need some help to get started? Consider reaching out to the Geomentor Community.