The Garth School in Spalding has gained funding for two new classrooms.
The cash comes from a £2.5million Department for Education grant to The Community Inclusive Trust, which also runs two special schools in Grantham.
The grant will also pay for supplementary accommodation, an administration area and a hall to accommodate the recent growth in pupil places.
This new stand-alone building will provide new Post 16 accommodation which will allow pupils to develop life skills.
The new accommodation will consist of classrooms, horticulture, cafe/kitchen and outdoor spaces to grow vegetables.
There will also be a new hall and staff room accommodation to assist the school in continuing to provide high quality education.
TRust chief executive Peter Bell said: “I am delighted that the Education Funding Agency (EFA) are supporting the outstanding provision we within its schools by investing in the future infrastructure.
“We want to play our part in providing the highest levels of education and care for children across Lincolnshire with all types of special educational needs.”