After one 18-year-old Potomac High School student made sure all was in order for him to walk across that stage, he was told he wasn’t eligible to graduate with his class because of an error by his counselor.

WASHINGTON — With less than one week to go before graduation, 18-year-old Delvin Tate Jr. got crushing news.

Despite working hard to achieve a 3.0 GPA and keeping up with his counselor to make sure all was in order for him to graduate from Potomac High school in Prince George’s County, Maryland, he was told he wasn’t eligible to graduate with his class.

Tate’s older brother and legal guardian Rashad Price got the initial phone call from Tate’s counselor.

Price said the counselor explained she had made an error — one that meant Tate couldn’t participate in graduation.

In April, she discovered that Tate was short of credit, but told him that if he enrolled in a technology course and did all the required work, he’d be on track to graduate.

She was wrong.

Price said he was stunned. As his younger brother’s guardian, he’d kept on the teenager about the importance of getting good grades and planning for his future.

“His third-quarter report card said he had met all requirements for graduation. There was no reason for me to believe that he wasn’t going to graduate,” Price said.

He appealed to administrators at the school.

“They felt bad for what happened — they just felt awful for my brother.”

But Price said they were firm: Tate couldn’t participate in graduation, even if he planned to complete his work in summer school.

Prince George’s County school spokesman John White said in a statement that in order to graduate, the Board of Education would have to certify that Tate met state requirements and because of the counselor’s error, he had not.

“If requirements have not been met, the Board of Education and school system cannot certify students as graduates,” White wrote.

Tate is not alone.

Another student at Potomac High school — with the same counselor as Tate — was in the same boat. Neither would be able to graduate.

White said the school system discovered another student at Oxon Hill High School was in a similar situation.

“Our focus is on supporting the students with meeting their requirements this summer,” White said. That means the school system would cover the cost of summer school.

Price said that did little to take away the bitter disappointment for his younger brother.

“The issue is that he misses out on his graduation ceremony with his peers,” Price said.

The school’s graduation ceremony is Wednesday morning.

Price said the letdown is compounded by the fact that Tate had worked so hard to make sure he was on track to walk across that stage to collect his diploma with his friends. Tate was willing to do the work in summer school, Price added.

“Being able to walk, participate, have his moment that he earned and worked hard for — then take the summer school class and move on — that’s all we want.”