The 17-year-old left Falmer high, an 11-16 secondary in Brighton, with seven A and four B grade GCSEs, to go into the private school's sixth form.
Sheena said: "When I said that I carried a clarinet case and books around and did not get bullied, that helped to break down the stereotype that state schools are rough, hard places."
"A lot of my friends thought I would change and become a snob, but it did not happen. I became involved in so many extra-curricular activities. It really is a 9-to-5 college, whereas in state schools you can go home at 1pm if you do not have any lessons."
Sheena, who is Mauritian, is predicted to get two As and a B at A-level and is hoping to go to Manchester university to read English. "The thing I miss about Falmer is that when something was good it really stood out.
Everything is wonderful all the time here, but it becomes the norm."