In Tennessee, an attack on a software vendor interrupted standardized testing this week and may have also caused delays in Mississippi. In Ohio, computers crashed statewide as students were getting ready to take that state’s tests. In New York, computers went down, too, affecting students in several ways, and in one New York school district, a superintendent slammed some of the questions.

It’s standardized-testing season, and problems are being reported in states across the country as millions of students sit down to take exams that may have important consequences for them and their teachers.

Every spring, states give standardized tests, and their results are used to determine whether students move on to the next grade or graduate. They are also used to evaluate how well teachers did in improving student achievement. And every spring, problems with computers, servers or the tests are raised, fueling concerns about the value of the results and whether too much importance is placed on them.

New York has been at the center of a national movement to opt out of tests — a movement started to protest the controversial use of standardized tests to evaluate teachers. In recent years, to protest the importance attached to the tests, at least 20 percent of children have refused to take New York’s standardized exams. It is not clear how many students opted out this year in New York and other states, but WSHU radio reported that nearly half of Long Island students eligible to take the tests refused the English Language Arts exam.

In Tennessee, WREG-TV reported that officials blamed testing delays on a “deliberate attack” on Questar Assessments, a company that administers the exams.

The American Institutes for Research, the testing vendor for Ohio, experienced problems with its log-in system for accessing tests, and delays were reported across the state.

New York had online delays, too, with its accountability tests, which are also administered by Questar. According to the Democrat & Chronicle newspaper in Rochester, N.Y., some students in grades three through eight could not log in while others had no choices for multiple-choice questions and some lost their computerized notes.

Superintendent Eric Byrne of the Rye City School District in New York sent a letter to families spelling out some of the problems, including some test passages. It said in part: “We feel the tests administered today contained text passages that were above the appropriate comprehension level for many students taking the tests. Furthermore, the questions about the text passages were poorly constructed, making it difficult for students to comprehend what was being asked of them.”

The New York State United Teachers union has been warning the state against moving quickly to put tests online, especially after Questar reported data breaches on some of last year’s tests. The New York State Department of Education issued a release in January saying that the breach affected a fraction of 1 percent of the test-takers. Parents and public education advocates have expressed concern that officials have not done enough to ensure student data privacy.