Old authentic scene - English high school

I used to work as a TA (teaching assistant) in an English high school. 
It was Thursday, lesson 1, Science in Year 10 (14-15 years old boys and girls). A class of 'mixed abilities': 15 girls and 3 boys. 

Three of the girls begin talking at once, asking several questions for the teacher. He is very popular and passionate about his subject but clearly struggles with discipline. At one point he can't stand it and loses (or not?) it:

"Girls, enough. STOP THAT VERBAL DIARRHOEA!'

Silence. They got it.