For shops, that’s the language equality law. Not sure about the justification, but it’s not that hard to have dual signs (and written Catalan is easy to grasp f

For shops, that’s the language equality law. Not sure about the justification, but it’s not that hard to have dual signs (and written Catalan is easy to grasp for Spanish speakers). This law was introduced some 10 years ago. For classes, IIRC it’s not mandatory (or wasn’t 15 years ago), just common. My chemistry teacher spoke only Spanish, and it was fine.