About 125 students who took the ACT college-admission test at a Los Angeles school are in limbo after their answer sheets were lost in transit, leaving them and their parents upset as testing officials scramble to locate the missing material.

It isn’t the first time ACT answer sheets have been lost—several other known incidents occurred in the past few years due to packages being lost or damaged during transport. But ACT spokesman Ed Colby said that it is “extremely rare” for the answer sheets to go missing. He said the company carefully tracks packages as about 5,000 test centers administer the ACT on an average national test date.

In the Los Angeles incident, Mr. Colby said that a package of answer sheets from an April 8 testing at University High School didn’t arrive at the company’s headquarters in Iowa. ACT is working with the test center supervisor and FedEx to locate the package, he said.

ACT says it will pay for a retake for the students, and that the company is working on scheduling a retest date for later this month, or students can take it on any other future test date. ACT had initially planned for students to be able to take the test during this Saturday’s scheduled testing day. Some parents balked at that, saying it didn’t provide much time for preparation.

Some parents say they are concerned that their children aren’t academically and mentally prepared to take the exam even later this month after going weeks without studying for it, and experiencing various emotions at having their scores lost. They are also concerned that the delay will affect deadlines for college and scholarships.