It's definitely a scam.
How do I know?
1) Phone call from them to my mobile via withheld number.
2) No phone number for the school underneath the address on the "contract".
3) All correspondence from them is via yahoo.es. Any real school would have it's own domain name and website.
4) Money transfer via Western Union, the criminal's favourite because it's not traceable and ID is not stringently checked at the receiver's end. Any real school would have a bank account with an IBAN number, or use VISA (the money sent is theirs and not yours and could be recovered).

Send these f****** nothing. Or if you do, tell the police that you want to catch a fraudster. It would work something like contacting police wherever you are, they would contact their counterparts in Sevilla and arrange for "Martin Edward" to collect the money from ONE specified WU office. Good luck!

But hey, if they've only scammed one or two people that'll be plenty for a bunch of crooks from Benin (where the scam originated from) and they'll shut down and move on to another operation. Probably already have done so.