Writing
This website has lots of resources for many subjects, and they are offering free packets weekly. There are great writing worksheets here called "Writing Challenge Workbooks."
Journaling is a fun, great way to practice writing. Children can write about anything in their journal, but this website has lots of great prompts for them to choose from.
This article has a lot of ideas for story writing prompts. You can give your child a story starter prompt and let them write a story.
This website has great informational/ argumentative essay prompts. Your child could write a paragraph on the topic, or turn it into a three to five paragraph essay.