Alfred Waterhouse and the meanings of symbols

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Hi all, I'm new here. I was walking through Hammersmith this weekend and was stopped dead in my tracks by this gorgeously romantic, terracotta building - which I correctly identified as gothic Victorian. I've done a bit of research and discovered that it was designed by Alfred Waterhouse and was part of St Paul's school (known as the High Master's House). The building is covered with various carved symbols - one in particular that I'm very interested in - and I very much want to learn the significance of these symbols.

Does anyone have any ideas where I might start? Does anyone know the building I'm referring to? I know there is a book about his terracotta designs, but I'm pretty sure that it covers the Natural History Museum and not anything else.

Thanks in advance for your comments!