AUSTIN—The state’s education boss is warning school superintendents that pizza parties, field trips and other rewards for students who pass the Texas Assessment of Knowledge and Skills may violate education privacy laws by inadvertently outing students who fail.

At most schools, the vast majority of students pass the test. Honoring them, by process of elimination, makes it easy to identify students who fail, Texas Education Commissioner Robert Scott wrote in a letter released Thursday to superintendents.

Scott said he recognized that motivational efforts are intended to encourage better performances on the test. But he said they have a negative effect on those who are not rewarded.

Texas Education Agency spokeswoman Debbie Ratcliffe said in a story in The Dallas Morning News that school assemblies recognizing students for passing the TAKS is technically a violation of the Family Educational Rights and Privacy Act.

“If you have 20 students in a room and single out 15 who passed the test, it’s pretty obvious who didn’t pass,” she said. “Principals aren’t intentionally trying to violate the privacy rights of children, they have just not thought through what they’re doing.”