If you'd like to set a pet free to make room for some new ones, take these steps:
1. Go to the game's login page and login to your student account by entering your username and password and selecting "Login".
2. Open the pet menu by selecting the paw icon from your toolbar:
3. Select the magnifying glass icon and then select one of your pets in order to see details about it. You can navigate through your complete collection of pets by selecting from the numbers along the top.
4. With the details menu opened, you can now release your pet by selecting "Set Free".
5. To complete the process, you'll need to confirm this by selecting "Yes". You can cancel this process and go back by selecting "No".
That's it! You'll now have some free space to catch new pets!