The county's third- and fifth-graders will continue to take the MSPAP.
Morgan said eighth-graders, knowing a new test will be in place next year, might not take the MSPAP tests seriously, producing "disastrous" results for the county.
Morgan said middle school principals oppose giving the test, parents might keep their children at home and score comparisons to previous years might be skewed because of a new scoring method in place this year.
The State Department of Education has given school systems that do not receive federal Title I money for middle schools the option of dropping the eighth-grade MSPAP tests. Washington County receives Title I money only for elementary schools.
Because teachers have been working to prepare students for the tests, Morgan said she recommended they be replaced with the CTBS to show results for that preparation.
"To forego any kind of accountability completely ... I think would be a shame," she said.
Morgan said the school system will be able to compare the eighth-grade results with those from across the country.
Director of Secondary Education Boyd J. Michael III said the CTBS will take two days to administer, compared to a week for MSPAP tests. The eighth-grade MSPAP tests were to be given from April 29 to May 3.
Ron Peiffer, an assistant state superintendent, said school systems are not required to replace the eighth-grade MSPAP with another test.
"They can do anything they want this year," Peiffer said. "Other systems are deciding not to do any alternative testing."
The MSPAP - or Maryland School Performance Assessment Program - measures the performance of schools, not of individual students. The CTBS measures individual performance.