Hi Massy,
im amazed the building contractor has even asked you for your input, ive witnessed projects like this before whereby the infrastructue is installed and they leave you to your own devises to "connect" up, failing this contractors need only offer a connection and as such put the cheapest equipment in.
Find out if there is a budget assigned and if so opt for the best you can, a couple of 48 port HP Procurves with 1Gb fibre modules should be your "entry level" within the New Build but you must also consider a 3rd unit placed within the old school to support the new fibre link running at a gig.
Ideally a new chassis based HP5412zl would sit nicely in the new build and would offer a reasonable amount of future expandability i.e 10Gb options, power over ethernet, managed wireless etc etc
Also you mentioned you have 100 x Cat6A segments installed thats impressive! 10Gb ready copper cabling to all areas make sure you get those all important test documents
Also find out the specification and number of cores of fibre you have had installed and once again I cant stress this enough dont forget those test results.
;-)