In Half-Blood Prince, we learn that there is a fund for students who lack money to be able to fund their school supplies:
‘I haven’t got any money,’ [said Tom Riddle]
‘That is easily remedied,’ said Dumbledore, drawing a leather money-pouch from his pocket. ‘There is a fund at Hogwarts for those who require assistance to buy books and robes. You might have to buy some of your spellbooks and so on second-hand, but –’
Half-Blood Prince - page 256 - Bloomsbury - Chapter 13, The Secret Riddle
The Weasley family is often shown as being quite poor and barely has enough money to buy school supplies (I recall that on one of their trips to Gringotts, they carefully searched each corner of their vault for a spare coin). Also, there wasn't enough money to buy Ron a new wand to replace his broken one until Arthur Weasley won some prize money to pay for it.
Would they have been eligible for this financial aid fund that was given to Tom Riddle? If so, why didn't they use it (were they too proud)?