Ground was broken Oct. 8 on the $63.8 million West Bridgewater Middle-Senior High School, with completion of the school expected by July 2015, and the athletic fields by the end of 2015, said School Building Committee chairman Gary Keith. CTA Construction of Waltham is general contractor for the 141,250-square-foot school, which is being built on athletic fields at the rear of the present school. Once the new building is completed, the old school will be demolished to make way for an artificial turf playing field, a six-lane track, a baseball field, and a field hockey overlay field. Because the existing fields can’t be used during construction, “even the home games will be away for a while,” said Keith. Residents voted to approve the new school and the fields last fall, and the Massachusetts School Building Authority will fund $29.4 million of the cost.