The day of her son’s eighth-grade promotion ceremony in Montgomery County, Susan Townsend got word that the teen had failed his Algebra 1 final exam. She says she was surprised, since he is a good test-taker and had a B average over his first three marking periods.

That same day, she said, she learned he needed to enroll in a summer session to get credit for his year-long course.

In a frantic change of plans, the family decided that the teen would forgo two weeks at a West Virginia camp with white-water rafting and zip lines, where he had been given a half-tuition scholarship. Instead, he signed on for algebra sessions at Montgomery Blair High School in Silver Spring.

“He was devastated,” Townsend said, recalling that the 14-year-old was partly packed and expected to leave in a matter of days.

The scrambled summer plans and disappointment also have come for others in Montgomery, where steep failure rates on countywide final exams in Algebra 1 have left people stunned. More than 5,300 students failed the final, including 82 percent of high-schoolers. For middle-school exam-takers — who tend to be high performers — the failure rate was 23 percent, nearly double the previous semester’s rate.

Montgomery school officials announced the poor results June 27 — two weeks after Townsend’s family changed their summer schedule. School leaders said they would add 15 percentage points to Algebra 1 final exam grades and offer free summer sessions for reteaching and retesting.

The recalculated scores spared nearly 1,400 Montgomery students from failing the exam, including Townsend’s son. But as summer school is under way at many schools, parents continue to wonder about the meaning of the low marks and what needs to be done to make up for learning gaps.

“Is the problem that they are not getting the content, or is it that the testing is not aligned with what they learned?” asked Catalina Schrader, whose daughter took the Algebra 1 exam in June as a middle school student. “By adding 15 points, do you really get to the problems or are you glossing over whatever the problem might be?”

Schrader said she is much less worried about final grades than about student understanding. “That’s where these kids are being short-shrifted, because if they didn’t learn what they needed to learn, they don’t have a base,” she said.

As part of the district’s late June announcement, Superintendent Joshua P. Starr wrote in a memo that the extra 15 points would bring failure rates into line with previous semesters in Montgomery and not penalize students for problems beyond their control.

Starr and other officials cited lost instructional time as a major cause of the spike in exam failures, saying teachers took time out to prepare students for state standardized tests that were required for graduation but were not aligned with course content. It was the first year that the Algebra 1 curriculum was based on Common Core State Standards.

Russ Rushton, head of the math department at Walt Whitman High School in Bethesda, said the new curriculum was a challenge because of its change in emphasis and sequence. But the lost instructional time — both for state test preparation and weather-related school closings — made for “almost a perfect storm” of difficulties and setbacks, he said.

At Silver Spring International Middle School, PTSA President Heather Powers Sauter says she has heard from many upset parents, including some who have rescheduled camps and summer travel to make room for algebra sessions.

Sauter said she took notice that one classroom teacher posted exam grades, without student names, showing that the highest score was 65 percent. Just four students earned passing grades before the 15-point adjustment.

“I was stunned,” she said.

Officials in Montgomery say middle-schoolers must pass the final to earn course credit for the high-school level class under state requirements. Districtwide, the extra 15 points meant 758 middle school students with failing exam grades were able to pass and earn the course credit.

Sauter said her school is offering an algebra academy, but she is particularly concerned about fallout for students who don’t get the benefit of summer school or extra support. “They’re going to end up in Algebra 2 and not have the foundation,” she said.

Others worry that the failures would perpetuate Montgomery’s long-standing problem with final exams in math.

Figures came to light last year showing that a majority of 30,000 high school students in key math courses failed their finals for fall semester. In Montgomery, most who fail exams do not fail the course; the countywide exams are worth 25 percent of the course grade.

“Just adding 15 points to a grade doesn’t mean anyone’s mastered the content,” said Jill Ortman-Fouse, a Silver Spring parent who is running for a school board seat and has a son who took the Algebra 1 exam at Takoma Park Middle School.

She said parents are still asking who should go to summer school and what low grades really mean. “There’s a lot of stress about it,” she said. “Parents want to make sure their kids are getting the building blocks they need for the next level of math.”

Montgomery officials said last week that school staff are following up with families of students who failed exams about enrolling in summer courses. Students who retest over the summer also will get 15 percentage points added to their exam grades.

For Townsend’s family, the exam grade diminished in urgency over time.

Townsend learned of the exam failure June 12 and found out about the 15 percentage point bump on June 27, when it was announced. By then, the teen’s parents had canceled his camp plans and enrolled him in algebra.

The family had no idea that there might have been problems with lost instructional time or material that did not get fully covered. The teen says he knew right away that the exam did not go well.

“There were things on it we never learned,” he said in an interview Saturday.

Still, with the boost in points, the teen’s exam grade improved to a D, and his course grade a B. He just completed his summer algebra, which he said helped. But he remains disappointed about the camp he missed. One of his friends, he said, lost the privilege of attending a concert because of a failed exam grade.

Lots of students who failed the test, he said, “had their summers changed in some way.”