Kicking off with a hard rock performance, it was clear this was not to be your average assembly.
At first students at Dunkerton High School, Iowa, seemed grateful for this musical break from the norm – albeit with Christian-themed lyrics denouncing the evils of drugs, alcohol and violence.
But things took a turn for the worse when the event veered into an impassioned and unfocused rant against homosexuality, abortion and sex before marriage.
After his band Junkyard Prophet left the stage, drummer and preacher Bradlee Dean took the microphone, separating the crowd into boys, girls and teachers.
Mr Dean is the president of the ministry You Can Run But You Cannot Hide International, which is listed by civil rights organisation the Southern Poverty Law Center as an active anti-gay hate group.
The clip above – a segment on homosexuality – shows him launching attacks on the influence of the media and pop culture, taking aim mainly at Sir Elton John and Lady Gaga.
Before a packed school hall he projects a photograph of Sir Elton next to a quotation that reads: ‘There’s nothing wrong with going to bed with someone of your own sex. I just think people should be very free with sex… They should draw the line at goats.’
Mr Dean demands of his young audience: ‘Is that a good moral standard? Would you allow your son or daughter to spend the night at Elton’s house?’
He then picks apart Lady Gaga hits such as The Fame and Born This Way, taking exception to her placing the lyrics ‘No matter black, white or beige’ side by side with ‘No matter gay, straight or bi’.
He says: ‘What she’s saying is if you’re black it’s the same thing as being gay. Sexual deviancy is the same thing.
‘You’re born as a product of your parents. But your actions – listen to this – you do have control over it.’
And after an embittered rant in which Mr Dean claims music videos give a false impression of what love is, he asks: ‘Did you know the average age death of a homosexual male is 42 years old?
‘Yeah, his actions literally kill him and he lives about half his life out.’
He adds: ‘Up until 1961 [homosexuality] was illegal in all 50 states. We protected that institution.
‘In 1998 if you were busted in Rhode Island you’d go to prison for 20 years; in 1973 they thought it was a mental illness.
‘Now what are they teaching you?’
Junkyard Prophet had previously visited the school without incident and staff were expecting them to return last week with a talk on bullying and making the right choices.
But instead, students found themselves faced with graphic images of aborted foetuses, while girls were instructed to obey their husbands.
Parent Jennifer Littlefield told the LaCrosse Tribune: ‘They told my daughter, the girls, that they were going to have mud on their wedding dresses if they weren’t virgins.’
Her 16-year-old daughter Alivia was distraught when she called her after the event and was one of several to have left in tears.
Appalled parents complained to the school, which has since accepted responsibility. The district authority is trying to recover the fee paid to Junkyard Prophet, who are said to command a rate of $1,500 (£955) per show.
Members of the group have since returned to the area to explain their performance, addressing 75 people at a nearby church.
According to local network KWWL, Mr Dean, who was met by a small group of protesters, took to the stage to hit out at ‘offensive’ accusations and negative media coverage.
He said: ‘When I left, there was nothing wrong with anything. I get home and it’s an anti-gay ministry.
‘I’m tired of that. It wasn’t brought up at all.’