I know ERPNext is basically used for enterprise . is it possible to customize ERPnext for making a application for education institution , managing the academic and examination modules ? If not, is there anything out there which would be a better alternative?
ERPNext has been used my universities, mainly to introduce ERP application to students.
If you requirement requires client side customization, you can achieve it using customization tools like Custom Doctype and Custom Script (client side).
You can also create custom application on Frappe for school management. Check following link to learn more about it.