Eight new classrooms have been opened at Spalding Academy.
Lincolnshire County Council spent more than £3 million for the new teaching block to be taken over by the business and geography departments.
The school has increased the number of Year 7 students it takes in from 270 to 300.
The building was officially opened by the Sir John Hayes MP and county and district council member Elizabeth Sneath who were joined by Matthew Stapleton (senior project manager at Lincolnshire County Council), Mrs Lucy Conley (South Lincolnshire Academies Trust chief executive officer), Mrs Jemma Curson (head of school) and Year 11 head students.
Sir John said: “Spalding Academy, a school I know so well and have backed throughout, has gone from strength to strength.
“This substantial investment will, by improving facilities available for pupils, secure the progress that has been made so far and promote even more.”
The building was designed to be environmentally friendly with large amounts of insulation and energy saving equipment such as ventilation systems and LED lighting to reflect the current best design in secondary education.
Mrs Conley said: “Our student numbers keep growing and it is therefore important we continue to provide outstanding teaching facilities for our students so they receive the best possible education we can provide.
“These new classrooms are just some of the improvements we have made to the school in the last two years and there are further new exciting building projects to be announced soon.”