David Wright, a high school technology teacher in Middletown, Delaware, has never taught reading or math. Even so, the state planned to judge his job performance partly on student test scores in those subjects.

That was until last month, when state officials said they would throw out a provision in a new system linking teacher performance to student achievement that assessed educators such as Wright on schoolwide performance in subjects they don’t teach.

“Judge me, fine, just let’s make sure it’s on things that I can control,” Wright, 34, and president of the local chapter of the state union, said in a phone interview. “In the rush to get it done as quickly as possible, they lost some of the logic.”

Delaware is in the vanguard of states developing new systems to evaluate teachers, according to Sandi Jacobs, vice president of the National Council on Teacher Quality, a nonprofit research and policy group in Washington. Delaware’s struggle may foreshadow complications that New York and other states face as they follow suit. Along with questions about fairness, states are encountering delays because of the complexity of tracking data, conflicts with teachers unions and concern from researchers that the entire effort could be misguided.

President Barack Obama’s administration has made tying teacher evaluation to student performance a centerpiece of its education agenda. Changing evaluations was a requirement for winning grants in the Education Department’s $5 billion Race to the Top program, of which Delaware was an early recipient.