You can use the same parent account for multiple children and over multiple school years.
To add a second child to your account, click on your profile icon in the top right corner of the game dashboard and select My Profile from the drop-down menu.
Then click the green "Add a Child" button on the lefthand side of your profile. You'll need to enter the parent code associated with the child to add them (you can get this code from your child's teacher).
Switching between classes and students
You can click on your child's name next to the Classcraft logo at the top to switch to a different child's character and view their progress.
If your child is playing Classcraft with the same character in multiple classes, you can also switch between their classes using the menu at the top of the screen.