East Bridgewater’s new junior/senior high school is on schedule to open in September. Project manager Simon Tempest told selectmen most windows have been installed, the final interior plastering and painting is underway, and bids for interior furniture and equipment have been received. The Massachusetts School Building Authority is reimbursing the town for around 65 percent of the $66.7 million in eligible costs for the project. The 160,542-square-foot school is based on the design of Whitman-Hanson Regional High School. The school will hold 950 students in grades 7 through 12.