My child has been there for 3+ years. It is still a good school. I disagree with many of the above negative comments.
Don't get me wrong, it is far from perfect and it is a very large inner city school, which comes with its own issues.
However, they have lots of opportunities and a great reward system. Yes it is strict and rightly so. I say you need to visit and trust your instincts, it isn't for everyone but in Westminster the options for boys are very limited and I still favour this school over all the other mixed or boys schools in Westminster. However, if you have a girl, I think Marylebone Girls is a better choice.
The school values attendance, punctuality, it is strict but caring when needed. Lots of clubs. The results are good and they offer more vocational GCSEs for the less academic children.
The school is calm, no students are hanging around corridors.
All schools will have issues, I have seen a lot of schools but when I revisit my choice, I would still stick with it. I am not saying there aren't better schools in London, absolutely there are but in Westminster, Harris remains my favourite after Marylebone Girls.
Absolutely worth a visit both for the morning and evening open days as they offer different perspectives (morning sees classes in action and evening shows what it can offer).