A programme of archaeological monitoring and recording was conducted during the groundworks for a new classroom block at The King's School, Brook Street, Grantham. An initial test pit was excavated at the western end of the classroom block's footprint, which was deemed less likely to have been impacted by prior modern development of the site. In response to the discovery of two pits of probable Late Medieval or early post-Medieval date, a larger area was stripped to the archaeological horizon. This exposed the foundations of three walls, two of which flanked a former culvert. A sherd of 17th-18th century pottery was recovered from between two stones of the western wall, and further Late Medieval to early post-Medieval pottery and animal bone was recovered from within the culvert itself. The third wall foundation lay to the south of the culvert, on a south-southwest to north-northeast alignment. Though no datable material was recovered from this feature, it appears to post-date the construction of the culvert and was tentatively given a 17th century date. {1}{2}