An Alabama teacher has been suspended after a geometry lesson on the best angles to assassinate President Obama

An Alabama teacher has been suspended after a national outcry for using an assassination attempt against President Obama to illustrate a maths problem to his class.

Gregory Harrison, the teacher at Corner High School in Jefferson County, Alabama, was to receive a slap on the wrist in the form of a "long conversation" with the local school authorities, after sparking a Secret Service investigation when he discussed possible angles to use in shooting at the president.

But officials only later decided they needed to take tougher action against Harrison following a flood of calls from people outraged at the lenient treatment. Harrison's deadly lesson was revealed this week by the local newspaper, Birmingham News, which reported:

The teacher was appar­ently teaching his geometry students about parallel lines and angles, officials said. He used the example of where to stand and aim if shooting Obama.

"He was talking about angles and said, 'If you're in this building, you would need to take this angle to shoot the president,'" said Joseph Brown, a senior in the geometry class.

Another student said: "We were going over a test and getting reviewed for our finals and were going over tangency. A student walked in and said, 'Well, if you shoot the president...' and the teacher picked up on it and said, 'OK, if you shoot off his ear, that is a point of tangency.'"

District schools superintendent Phil Hammonds said Harrison had shown a lack of judgment and was now suspended pending further investigation. "As a district, we are embarrassed by his actions and what he said. There is nothing that can be said to rationalise what was said. We take this very seriously. There is no place in our society for a person to make these comments," Hammonds said.

Before the flood of complaints, however, Birmingham News reported that Hammonds's initial response was: "We are going to have a long conversation with him about what's appropriate."

The Secret Service confirmed that it investigated Harrison before the story was made public, saying: "We did not find a credible threat."

Malia Drummond, a student in Harrison's class during the lesson, defended him as an conscientious teacher who didn't deserve to be fired. She told Birmingham News: "Yeah, the comment was probably inappropriate, but who in America hasn't make a joke about Obama? They make it sound like he was plotting an assassination, but it wasn't like that."