MANATEE — Three district high schools earned ‘A’ school grades for the 2011-12 school year, and no Manatee County high school earned less than a ‘C,’ according to preliminary data released by the Florida Department of Education on Friday.

The data show that Braden River, Lakewood Ranch and Manatee high schools earned A grades for the last school year. Southeast and Bayshore High Schools earned B grades, missing the top distinction by 1 and 17 points, respectively. Palmetto High School raised its grade from a D to a C.

The only district school that did not see improvement was Manatee School for the Arts, which fell from an A to a B.

“No D’s,” said Mike McCann, district supervisor of Dropout Prevention & Alternative Education. “Fantastic.”

The state department also reported statewide gains in accountability grades; 231 Florida high schools and combination high schools earned the A distinction this year.

The criteria includes FCAT scores, as well the school’s graduation rate, Advanced Placement students, and the results of SAT and other college placement tests, among other things. Also measured is the graduation rate of an at-risk cohort of students who are tracked starting in eighth grade because of poor FCAT scores.