A 13-year-old boy has been arrested on suspicion of arson at the old school building in Crowland.
The blaze ripped through the grade two listed Postland Road building in the early hours of June 7 last year – causing £100,000 worth of damage.
A team of 30 firemen had to be called to the site, which is near the St Guthlac School and the Abbey 345 Playgroup, to fight the flames as they ripped through three rooms on the first floor and destroyed much of the roof.
The incident was later revealed to be arson and police have this week arrested a 13-year-old youth from Crowland in connection with the fire.
He has been released on police bail until March 12 while officers conduct further inquiries.
The former school building is owned by Lincolnshire County Council. It was once turned into accommodation but was out of action when the arson attack took place.