How do I get all messages, and the ClassroomParent site, in Spanish automatically?
The easiest way is from a message email. Click the en Español link at the top of the email. Below the translated message, you'll be asked whether you would like all future messages, as well as the ClassroomParent site, shown in Spanish. Click the button to say yes, and your language setting is updated right away.
The same works in the other direction: if your messages arrive in Spanish, the link says In English, and the button switches everything to English.
If you don't see the question, your language setting already matches the language of the page.