Great find.
Do we know when it moved to narrow down the time frame?
The school,was founded in 1977. New address is 1 Waterloo, side street is Canton. I’m not finding when they moved but it had to be after Google maps made their way around with their cameras as there is no signage at the current address.
And looking at Google maps image of Canton and Nelson streets, it sure looks like the initial “Find Snowden” picture from drop #869 on March 7th. Plus the skyscraper at the end of Nelson Street would offer the vantage point the Snowden pic was taken from.