Thetford Grammar School is an independent co-educational school in Thetford, Norfolk, England. The school might date back to the 7th century, which would make it one of the oldest schools in the United Kingdom.

The school website conjectures its origin traces back to 631, and through its Roll of Headmasters to 1114. The Independent Schools Inspectorate assert in their 2012 report that "The school was originally founded in the 10th Century" but without any evidence provided. It appears to have ceased from around 1496 until its refoundation from the will of Sir Richard Fulmerston in 1566. The refoundation was confirmed by an Act of Parliament in 1610. Part of the school is built on the site of a thirteenth-century Dominican Friary, which was built on, and incorporated parts of, the Norman cathedral. This building, now known as "Old School", comprised the entire school for about 300 years, and is where Roger North and Thomas Paine were educated.

Thetford Grammar School strengthened its academic impact abroad with the opening of TGS Prep Shanghai and we opened a pre-GCSE and pre-A level learning centre in Xi’an. The HR on this website is dedicated to recruiting high-quality, reliable and responsible native English speaking teaching staff for the centre in Xi'an.