A Microsoft file hosting and synchronization service.
Dear Saurabh Mete,
Greetings! Thank you for posting in Microsoft Community.
Per your description, your 1 TB OneDrive storage reduced to 100 GB.
The situation you experienced is related to Program Updates in Microsoft 365 for Education - Microsoft Community Hub
Effective February 1, 2024, users of Office 365 A1 (no-cost subscription) will be limited to a maximum of 100GB of OneDrive storage per user within the school tenant’s 100TB of pooled storage.
You may go to contact the Microsoft 365 Administrator in your school, they can purchase A3 or A5 licenses and then assign more OneDrive storage to your account.
For reference:
How do I find my Microsoft 365 admin? - Microsoft Support
Storage Changes for Microsoft 365 Education | Microsoft Education
Appreciate your patience and understanding and thank you for your time and cooperation!
I hope you're staying safe and well.
Sincerely,
Tina | Microsoft Community Moderator