The easiest thing is going to your User Management section, changing the students' passwords and try again.
Log in with your teacher login details and go to your User Management section. You can find the student accounts and change the passwords there. Go to the student account you want to update and choose Update.
We don't support IE 8 or older. This might be the reason you can't log in.
Students can only play for free and participate in the competition between 7 AM - 2 PM. Outside of these hours, the accounts do not work.