Damers First School is an existing school in Dorchester but is being relocated to the estate to cater for an extra 150 pupils.
It will be the first school in Poundbury, a so-called "model town" that was started in the 1990s.
The new school, which will cost about Â£10m, is expected to be finished in December 2016.
Pupils and staff will move to their new premises in the spring of 2017.
Its capacity will rise from 450 to 600 pupils to accommodate what Dorset County Council calls a "significant rise" in its school-age population.
Trevor Jones, county councillor for Dorchester, said: "It's all taken a long time but I'm delighted that we're nearly there."
Work has started on a new primary school on Prince Charles's Poundbury estate in Dorset.