Annoyed at a recent federal ruling that could nullify the credentials of thousands of public school teachers, Texas education advocates want Washington to waive a technicality they say would cause teachers and districts needless headaches.

At the same time, the Texas Education Agency's original estimate this week that 30,000 teachers would be affected now appears way off — on the high side. And a federal spokeswoman signaled that the state would be given little leeway.

At issue are the credentials of many newly hired elementary teachers, who were told before the school year they met the federal requirements to ...