The building has been three years in the making and is helping the school cope with an increase in the local birth rate which has seen an extra 10 children a year welcomed into the Reception class.
Head John Ross said the plans were first formed three years ago.
He said: “The school started taking in 60 children instead of 50 because of the increase in population in the area. We were already over capacity in the school prior to that.
“Lancashire County Council recognised that population increase and asked if we would take more children if they built us more classrooms.
“They have been tremendous and worked with the school to design a great space for the children which has freed up space within the main school. I think the council should be congratulated for thinking ahead and planning for the future.”
Planning and building work has been going on for over three years and stalled last summer when Askam Construction went into receivership. However, John Turner’s continued the work, and the classrooms – which all have giant screen interactive TVs – are finally being used by the children.
An official opening will be held at a later date, but a small ceremony was recently held to let the children explore the new space. The school’s longest serving teacher, Mrs Bartlett, and the longest serving teaching assistant, Mrs Hayward, cut a ribbon.
The new classrooms house children in Reception, Year 1 and Year 2.
And within a week of opening, the extension was used as a polling station during the general and local elections.
Great Wood, in Beaufort Road, is now home to 380 children, and in four years this will rise to a maximum number of 420.
The building work will also allow other rooms to be used for different purposes, meaning the children can soon enjoy a new library and computer and community rooms.
Great Wood is holding an open morning for prospective parents on June 17, 9.30-11.30am.