School at Home for 11+
This section is specifically for school or homeschool type resources; but remember that children will learn a lot from other activities too. If you are doing 'school work' at home remember that the actual working time will a lot shorter than when they're at school. This is because a certain amount of school time is taken up with group working skills, social skills and personal development.
Some of these resources are regularly free and there are some homeschooling and other web businesses which have made their resources free for the next few months in order to help out.
Especially good for maths and computing for all ages but other subjects at Secondary level. Note this uses the U.S. grade system but it's mostly common material.
Free to access 100s of courses, only pay to upgrade if you need a certificate in your name (own account from age 14+ but younger learners can use a parent account).
For those revising at GCSE or A level. Tons of free revision content. Paid access to higher level material.
Free taster courses aimed at those considering Open University but everyone can access it. Adult level, but some e.g. nature and environment courses could well be of interest to young people.
Aimed at Secondary age. Multi disciplinary activities.
BBC Bitesize has just released a huge comprehensive resource with lessons each day for every age group on their website. There is also an accompanying podcast for 10 minutes or so every morning to help you to plan your day.
"Create stories, games and animations and share with others around the world." Scratch is a well known block coding website made by the famous MIT in American. It is free, quite straight forward to use, easy to set up an account and there are lots of suggested projects online. Your child may also be using it in school and have learned a bit about it already. Suitable for children from about 6 to 18.