Login to student panel via URL http://yourdomain/site/userlogin. If student belongs to multiple classes then you need to choose your class (If you are login as Parent and you have more than one child then it will show you all the classes of all children) from the given modal, system will store your selected class as your default class (when you login next time it will process with this default class), Later on you can switch your class from the Class Switcher present at the top right corner.

student login image