WebEnglish.se has everything you need for your B1-level students (even lower and higher) to keep learning at home, while their school is closed. Here are my personal recommendations:
Audiobooks. Reading is the best way of learning a language and with audiobooks the reader can listen to natural language at the same time as reading the text.
Real Books. There are loads of books free to read on the net nowadays. Here are three good pages for the students to choose their favourite from: AllNovel.net, Novel12.com, and Classic Books.
Themes. Students can choose a theme they are interested in, learn about it through the activities and make their own presentation of what they have learned.
Learning 1:1. Here is a collection of websites for the students who would like to choose what to work with, including listening, reading, writing and vocabulary. Some are game-oriented.
Google. If your school has Google accounts, there are many ways of using Google that you may not have thought of. Find new ideas from these pages.
Teen Beginners. You can assign a theme for your teen beginner students, where they can study the vocabulary, view the videos and learn the dialogues on their own. They can also follow an online course by themselves.