Smartschool Calendar can be integrate into HA by using the iCal url exported from Smartschool (Smartschool > Schoolcalendar > Export). This iCal can be loaded into Home Assistant using the “Remote Calendar” default integration.
I recently developed a new integration to connect Smartschool into Home Assistant with a custom integration (should soon become availbalbe via HACS): https://github.com/myTselection/smartschool_ha
The main incentive of this integration was to get a clear overview of all outstanding tasks and being able to mark these as completed.
I didn’t now the calendar of smartschool could be exported and loaded into Home Assistant, so still further experimenting with it.