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.
This site is old and no longer updated and yet there's so much still available, from language learning to BBC Bitesize for revision. No TV licence required except for content on BBC iPlayer.
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.
Learn computer programming skills - fun and free.
Creative computer programming
All sorts of engaging educational videos
National Geographic Kids
Activities and quizzes for younger kids.
Learn languages for free. Web or app.
Free science lessons
The Kids Should See This
Wide range of cool educational videos
You Tube videos on many subjects
Crash Course Kids
As above for a younger audience
Science awards you can complete from home.
Digital enterprise award scheme you can complete online.
Paw Print Badges
Free challenge packs and other downloads. Many activities can be completed indoors. Badges cost but are optional.
All kinds of making.
Is in U.S. grades, but good for UK Primary age.
Listening activities for the younger ones.
A lot of these can be done in a garden, or if you can get to a remote forest location!
Resources for English language learning
Oxford Owl for Home
Lots of free resources for Primary age
Big History Project
Aimed at Secondary age. Multi disciplinary activities.
Blue Peter Badges
If you have a stamp and a nearby post box.
The Artful Parent
Good, free art activities
Red Ted Art
Easy arts and crafts for little ones
The Imagination Tree
Creative art and craft activities for the very youngest.
Educational online games
DK Find Out
Activities and quizzes
This is more for printouts, and usually at a fee, but they are offering a month of free access to parents in the event of school closures.