Samantha Yeoman, the former head at Rogerstone Primary School, is accused of allowing teachers to see exam papers before the tests and giving pupils extra time to complete them.
Ms Yeoman resigned from her post last year, the conduct hearing was told.
Her counsel said she was not leading the tests at the time.
Gwylim Roberts-Harry told the hearing on Monday his client only became aware of "certain elements" after the tests.
The panel heard she allowed staff to manipulate the 2013 National Reading and Numeracy Test results, so pupils would achieve better grades.
The school's deputy head teacher, Wayne Millard, told the hearing Miss Yeoman returned from a conference, where she said the majority of teachers indicated they had been shown the test papers.
He said Miss Yeoman "became angry" when she found out her teachers had not been shown the tests. He said a timetable was then drawn up for them to view them.
The panel was also told of claims pupils were called back to change wrong answers on their test papers.
A complaint was also made by a parent who claimed the way tables were arranged in her daughter's class meant she could see the test answers on her teacher's desk.
Miss Yeoman is also alleged to have applied undue pressure on staff by agreeing unrealistic standards, and creating a threatening and intimidating work environment for staff.
She denies unacceptable professional conduct and did not attend the hearing.
Evidence is expected to continue for the rest of the week.
A former Newport primary school head teacher allowed staff to manipulate national test results, a General Teaching Council for Wales panel heard.