Eco-Schools is a global programme engaging 19.5 million children across 67 countries, making it the largest educational programme on the planet. Primary and secondary, college etc all ages. Takes a year and is pupil lead.
Managed by Keep Britain Tidy in UK. Schools get a green award at the end and are provided with free resources. Internationally recognised. 
For nearly 25 years Eco-Schools has been empowering children to drive change and improve their environmental awareness through the simple Seven-Step framework in order to achieve the international Eco-Schools Green Flag award.
Eco-Schools develops pupils’ skills, raises environmental awareness, improves the school environment and creates financial savings for schools as well as a whole host of other benefits.

SKIPS publish fun homework books which are toolkits to take messages to parents and engage them with this subject and to persuade them to start saving energy, saving money and throwing away less waste in their homes and while supporting the learning of their children.

Excellent website that included pdfs you can download, lessons plans and resources for different age groups and on different themes. They highlight the school subjects the plans match with. 
Ages 5-7, 7-11, 11-14
Themes: Climate Change, Species and Nature, Food and Growing

SEEd is a registered charity that identifies, promotes, enables and supports environmental education and education for sustainable development in the UK. It is an umbrella, membership organisation for Non-Government Organisations (NGOs), schools, colleges, universities, local authorities and educators interested in Environmental Education and ESD and the environment.

Provides information, advice and activities for primary and secondary schools. It also guides you through the process of setting up and maintaining effective recycling schemes. 

Keep Britain Tidy runs the international Eco-Schools programme in England and is all about getting school communities to be more sustainable. 

Offers information for pupils and teachers, key stage activities, games and facts.

LEEF is a networking organisation that aims to support, facilitate and promote environmental education across London. It organises training workshops and events and circulate information to raise the profile of environmental education within the media. 

For the past few years, environmental charity, ecoACTIVE, have worked with primary children to teach them about waste prevention and recycling. They produced an education pack including curriculum-linked lesson plans for all the activities they have been running in schools. 

Circus Takeaway run Theatre in Education shows and workshops in schools. Each show has its own enticing backdrops, props and unique costumes. Shows always involve juggling, magic, physical skills, comedy and songs. 

Art in Education delivers dynamic, imaginative and multi-disciplinary creative education projects for a diverse range of people including toddlers, special needs individuals, young people, artists, adults, and the general public.

WRAP is a registered charity that works with businesses, individuals and communities to achieve a "circular economy" by helping them reduce waste, develop sustainable products and use resources in an efficient way. They have a huge online database of free resources for schools including lessons plans, artwork and teacher packs

TTS are a Midlands based supplier of educational materials.  This ideas page pulls together some ideas for practical "eco-school" projects around waste, recycling and growing

World (originally Walsall) Against single Use Plastic is a network of schools and organisations cleaning up green, blue and grey space.  Over thirty schools are part of WASUP.  

We bring waste education to life with exciting films, media-rich resources and campaigns designed to inform, inspire and empower children to care for the environment.

Our mission is to enable young people to fulfil their potential by providing resources and support to schools to engage them in environmental projects.  We build their skills and aspirations while encouraging them, their community and wider society to live in a more sustainable way.

Our mission is "to bring an Ecoed culture alive: to open up the possibility for individuals, families and organisations to engage in taking action to tackle some of the biggest challenges of our times, by changing that which is within arms' reach - our own daily choices and habits - and to do so in a positive way."

Our mission is to connect and empower schools worldwide to lead the transformation to a sustainable future.  We are an alliance working together to nurture and fortify sustainable school communities. 

We believe that the next generation is key to society becoming sustainable fast enough, so we provide energy and carbon literacy education to students funded by solar panels on each school.

Forest Schools Birmingham was founded in 2004 in response to the increasing demand from schools for quality Outdoor Learning, Forest Schools provision, Teacher Training/INSET  and innovative Schools Grounds Design in an urban environment.

Much of our work is aimed at establishing food-growing as a centrepiece to the activities of schools. We aim to educate children about the value of food-growing with a view to bringing about environmental, health, social and financial benefits.

Food for Life brings schools, nurseries, hospitals and care homes, and their surrounding communities together around the core ethos of healthy, tasty and sustainable food. Our School Award supports schools to take a whole school approach that sees them grow their own food; organise trips to farms; provide cooking and growing clubs for pupils and their families; serve freshly prepared, well-sourced meals and provide an attractive dining environment.

We are a national network for parents and carers that will promote understanding of the key issues around air pollution.  We offer resources and support to help you to get involved in whatever way you can.  

Modeshift STARS is a national award scheme which offers support and rewards to schools for taking steps to promote safer, greener, healthier travel. By participating in the scheme your school will be able to produce a new national standard School Travel Plan with an achievable action plan. Details of the Birmingham Council scheme here. 

Climate Box resources provide students with information on issues related to climate change in an interesting attractive and entertaining way, plus recommendations to teachers on using the toolkit in the school curriculum. 

Eco clubs in schools will empower students to participate and take up meaningful environmental activities and projects. It is a forum through which students can reach out to influence, engage their parents and neighborhood communities to promote sound environmental behavior.

A ground-breaking, £6.4million project funded by the Department for Education with support from the Department for Environment, Food & Rural Affairs (DEFRA) and Natural England.  Over the duration of the four-year project thousands of children will be given the opportunity to get closer to nature which will benefit their learning, health and wellbeing.

School Plates by ProVegUK helps schools across the UK improve the health of their pupils, save money and help save the planet.  Working with schools, local councils and catering companies, we are improving school menus across the UK. Schools are encouraged to adopt 5 asks which are simple and effective ways to increase the intake of vegetables, fruits and other plant-based foods.

Teach the Future is the UK Student Climate Network (UKSCN) and Students Organising for Sustainability (SOS-UK) joint campaign to repurpose the education system around the climate emergency and ecological crisis.  Their campaign includes a set of asks of schools and national government.  Click the "Learn More" button to go to their web site, or download their detailed document (PDF file) here.