The pupils, from Wooler Middle School, were starting the creation of the forest on the 354-hectare Doddington North Moor site 7km north of Wooler.
In all, 42% of the site will be planted with productive conifers, mainly Sitka spruce, with 20% going to native broadleaves and 13% to mixed natives including Scots pine. A further 10% will remain as open ground and 15% as managed priority habitat, include the restoration of a rare peat mire.
Trees have been provided by two nearby nurseries, Cheviot Trees of Berwickshire and Trees Please near Hexham.
Around 65,000 trees are due to be planted by the end of April, with the rest following over the next two seasons. Though approved on 30 November, planting has has had to wait for preparation work including clearing vegetation, putting up deer fences and mounding, which were delayed by the recent harsh weather.
As well as establishing a future timber supply to local processors, the work will also create new mountain bike trails, opportunities for forest education and improved access to a bouldering site.
Project manager Andy Howard of Pennine Forestry, whose two children took part in today's planting, said: "I hope Doddington can be a blueprint to help develop the resources future generations will need, and to restore and maintain some of the biodiversity we have lost."
In November, Howard told a land use conference: "Doddington has hopefully broken the mould and can help us start to move away from the ridiculous position where you have to prove that planting trees is not a bad thing.
"You have to be prepared to challenge the 'Defra family' and their understanding, you have to plan very carefully, talk to local people at a very early stage and adhere closely to the UK Forest Standard."
Local Conservative MP Anne-Marie Trevelyan and North-East England Labour MEP Paul Brannen, both supporters of the project, also attended today's planting.
Brannen said: "The new forest at Doddington is both a good and bad news story – good in that new forests can make a significant contribution to tackling climate change as the trees absorb carbon, but bad in that Doddington has again proved that new forests are far too difficult to get permission to plant.
"Let’s hope this new forest is the first of many and not the last of far too few."
Forestry Commission director of forest services Richard Greenhous said: "Doddington has served as a learning experience for all of us, informing future processes and leading us closer towards achieving the government and forestry sector’s ambitions to plant more trees in this country.
"We’ve worked hand in hand with the applicant, Natural England and the Environment Agency to get to this major milestone, and stand ready to support other landowners by helping them receive the benefits of woodland creation."
Forestry trade body Confor chief executive Stuart Goodall added: "This is a tremendous day for forestry in England.
"Andy has had to work his way through a really challenging and complex set of rules for forest creation, designed for a different generation. He has broken the mould and others following in his wake will reap the rewards of his efforts."