Pupils have returned to Cwmcarn High School 14 months after it was closed down because of asbestos.
The school had been due to open its doors again in September, but the death of an asbestos contractor on the site delayed the work.
Staff and pupils have held a special celebratory assembly to mark the first day back.
In a letter to parents, headteacher Jacqui Peplinski said: “I would like to take this opportunity to thank you once again for your patience and support throughout this challenging time. It is time to put the last thirteen months behind us and to return to business as usual; we are back in our community and stronger than ever.”
The school shut in October 2012 after the discovery of asbestos by contractors and its 900 pupils have since been taught at Coleg Gwent’s Ebbw Vale campus.
Caerphilly County Borough Council agreed to spend £1 million on removing the asbestos but there were several public rows between the school and the council over the cost and type of work to be carried out.
The school’s reopening was originally planned for September last year but the death of a contractor delayed the reopening twice.
In July last year James Paul, 26, from Abertillery, was killed at the school while working in a suspended ceiling void. His death is currently under investigation by the Health and Safety Executive.