Yet the result has been a roaring success which has won the school a place on stage at the National Theatre in London in a competition backed by British Telecom to the tune of pounds 400,000.
A dozen playwrights, including Wole Soyinka and Liz Lochhead, were commissioned to write new works specially for young people. Nearly 150 youth theatre companies chose one of them to perform and one production of each has been selected for the showcase at the National on South Bank in July.
Mr Lonsdale, Sandbach's deputy head, originally shied away from Bryony Lavery's play More Light because it was for an all-women cast. But as he perused the scripts he had to choose from, he realised it would not be as inappropriate as he first thought.
Adopting the distinctive style of the Peking Opera, which is performed by men only, the boys were soon won over to the story of women forced to adapt to their tomb home. They respond to necessity by consuming the emperor's body.
Mr Lonsdale said that there were a few giggles in early rehearsals, but they were quickly overcome. "It's been a wonderful learning experience," he said. "What we said in entering [the competition] was whatever we did, we were prepared to take risks. I was staggered by how the boys adapted."
One of the cast, Rob Cox, 17, said that playing a concubine was certainly challenging, but had been very interesting. "It's nothing like we've tried before. It's been wonderful."
David Critchley, 14, who plays Pure Joy, another of the women in the play, said he was "gobsmacked" when he was first told what they were to do. "I wondered what they had chosen. But I really enjoyed it. I just like the difference of it - acting as a woman and being a woman."
Suzy Graham-Adriani, the National Theatre's youth theatre projects producer, said the scheme, called BT National Connections, was a first. "Up to now you could count on the fingers of one hand plays written for young performers," she said.
"Adult writers don't automatically write for young performers. But the idea is that this is encouraging young people to have an active interest in theatre by having good scripts to work with. It's making theatre as high-profile and sexy as we can."
Ms Lavery said she was very pleased Sandbach had found a way to perform her play.
"It's a very coherent production and really moving and lovely," she said.
"The play has had a hammering because it's about sex and death and all those things, but I'm absolutely convinced young people need serious work. They work their socks off with huge amount of energy and produce beautiful acting."