Carver schools are “basking in the largest gains” in the south-of-Boston region posted by its Grade 10 students on last spring’s MCAS tests, school Superintendent Elizabeth Sorrell said last week. Grade 10 students increased scores over the previous year in all three areas tested. The percentage of students in the proficient or advanced categories rose to 96 from 85 in English; to 87 percent from 78 percent in math, and to 73 percent from 56 percent in science. Sorrell called the results “the rewards of strategic improvement strategies” and attributed the district’s strong academic performance on the statewide tests to rigor in the classroom, professional development for teachers, and responsive feedback to teachers and students. “Increased student learning is our primary focus,” Sorrell said.