When the advanced-skills teacher uses music in his classroom at Forest Hill comprehensive, in Lewisham, south London, he plays contemporary soul from his own collection. When he is hungry, Mr Ellis takes crisps from a pupil.
And, in the past, he has arm-wrestled with pupils.
"It's all a calculated risk," said the 37-year-old. "It makes the kids think, hey, this guy is human."
Mr Ellis's charismatic, if unorthodox, teaching style is to appear shortly on prime-time TV, as part of a one-off BBC documentary, entitled School Day.
For one day in January, a dozen film crews trailed heads, new and experienced teachers, all with diverse teaching styles, to highlight the multi-faceted nature of British education.
Steve Greenwood, the programme's producer, said: "Millions of people troop off to school every day but very few of us have any idea what happens once they are there. This is an observational film. It's not Hollywood. We show normal people doing normal jobs."
School Day will be shown onBBC1 on May 12 at 10.35pm.