Parents can buy instruments without VAT but looking at the Suffolk LEA website it seems pointless doing this. Firstly it takes time, you have to choose the instrument, then ask your LEA to buy it from the shop who deliver it to the LEA up to four weeks later, pay the invoice sent by the LEA and then collect the instrument from the school.
This is a totally pointless and overly complicated scheme. Why can't schools just give named pupils a voucher or certificate that the music shop can pass to HMRC to certify their sale was exempt from VAT.
There is an Arts Council England scheme which makes interest free loans (0% APR) of up to £2000 for musical instruments.