Hola Spid,
When you fly from A to B, even with perfect weather conditions and an airplane you know very well, things can go wrong, e.g. weather, technical malfunction, toilet etc.
Unless you are dealing with one of the big flight schools with airline connections such as L-3, Jerez or CAE (and even then I would be careful), it is too risky to part with that money at this early stage. What if you lose your medical next year, you don't like the school or the instructors, the school goes bankrupt, you want to give up everything for a girl etc.? Once, I was even told about a situation in which a maintenance organisation got its part-145 certificate revoked and a flight school had all of a sudden part of its fleet grounded. Students couldn't fly for a few weeks and it was not the school's fault. Bottom line is that a lot of things can happen after giving up that money and in the end, it is nobody's fault, an act of God.
I understand that you might want to learn at that school though. Hence, if I were on your shoes, I would be open to the school, make clear that you have and want to give them that money and suggest something along the lines of paying their administrative fee plus theory plus the first 10 flight hours in advance. Paying (in advance) as you go might be acceptable since in this case, there is not much to lose for them. If later something goes wrong during your journey, you do lose money, but it is a managed risk.
If your preferred flight school is in Spain, you will know that many of these schools are currently looking for students. Use this for your own benefit! :-)