School ratings released late Friday also showed that 20 percent fewer Delaware schools received a "superior" designation ranking from the Delaware Department of Education. At the same time, the number of schools slated for "academic review" and deemed "under improvement" increased.
Schools listed as "under improvement" can be mandated to offer free tutoring or to restructure.
Delaware Education Secretary Lillian Lowery says the state has to take major steps to "radically" improve its education system.
Gov. Jack Markell signed a new law Friday that requires teachers to show two years of student growth within three years to receive tenure.