WILMINGTON — Gov. Jack Markell vetoed the “Opt Out” bill Thursday that would have allowed Delaware parents to pull their children out of standardized testing in schools.

Advocates for House Bill 50 had said the legislation asserts parental rights and that the assessments put unnecessary pressure on students and teachers.

In his veto statement, Gov. Markell, a Democrat, said he agrees that schools need to cut back on testing. But, he added that he thinks the annual state assessment provides “important information” for teachers and school leaders to determine where students are excelling or need extra help.

The tests also help evaluate the effectiveness of the more than $1 billion in state funds directed to the education system, Gov. Markell said.

“HB 50 would undermine the only objective tool we have to understand whether our children are learning and our schools are improving,” he wrote in his statement.

“It has the potential to marginalize our highest-need students, threaten tens of millions of dollars of federal funding, and undermine our state’s economic competitiveness — all without adequately addressing the issues that motivated many to support the legislation.”

Sen. Dave Lawson, R-Marydel, a co-prime sponsor of the bill, said in response to the governor’s veto that parents have the right and responsibility to look out for the best interests of their children.

“This action by Gov. Markell proves, without a doubt, that he and the ‘We know best’ bunch have NO regard for what parents and the legislature approve.

“It is sad that the Governor decided to veto a piece of legislation supporting parents’ rights,” he added.

Gov. Markell had opposed the bill since the beginning, but the measure passed the House by a 31-vote and the Senate by 15-6 vote.

The governor instead proposed taking an “inventory” of all standardized tests administered at the state and district level.

He signed a resolution Thursday which will bring together legislators and other key groups to review the inventory and make recommendations about which assessments to cut.

They are required to publicly report the final results by June 2016.

“While I believe strongly in the value of a universal statewide assessment to tell us whether our students are making progress, the first priority of our schools must be to ensure that our students have the time they need to learn,” Gov. Markell stated.

“But to address that concern, we should not be encouraging certain students to opt out of a test that provides valuable information — we should eliminate entire tests for all of our children and put that time to work in the classroom.”