I'm developing app using MS Graph Education API and able to create school and add user in this school. But I can't find this created school in dashboard.
Shouldn't it visible in that dashboard?
The Education API creates the schools as AAD administrative units. The Intune for Education portal was designed to work with School Data Sync, which creates the same types of objects as the Education API, but also creates a security group for the school. To get your school to show up in the Intune for Education portal, just create a security group as well for that school.
(Edit: Adding comment reply here since comment formatting on SO is just terrible)
You can tag the group with your school's ID. Here are the properties that SDS sets on the school security groups it creates. In this case, it's tagging a SG to be associated with the school whose "externalId" is "10001".
"extension_fe2174665583431c953114ff7268b7b3_Education_ObjectType": "SchoolSG",
"extension_fe2174665583431c953114ff7268b7b3_Education_AnchorId": "SchoolSG_10001",
"extension_fe2174665583431c953114ff7268b7b3_Education_SyncSource_SchoolId": "10001"