The FBI said it is investigating after a top Rhode Island high school’s website was hacked by someone who left a pro-Islamic State message. Classical High School in Providence is a magnet school and one of the most prestigious high schools in the state. Its website was taken over Saturday by someone who said the site had been hacked by ‘‘Team System Dz’’ and messages including ‘‘I love jihad’’ and ‘‘I love isis.’’ An FBI spokeswoman on Monday said they are investigating. Providence school spokeswoman Christina O’Reilly said city police are also investigating. O’Reilly said no personal information was on the site.