This Head Teacher needs re-educating to act responsively, you do not ask parents to buy something for their children by asking the children first, you correspond with the parents directly.
As to whether, the question should have been asked in the first place is questionable. Why are they required, what will be the advantage, and more need to be considered.  How will their use affect the teaching within school, is it replacing some lessons or creating additional lessons and will any teachers be made redundant.
On the face of it a very ill thought idea, which needs to be rethought or withdrawn.