Schools, community halls etc NEVER had or have any money, so consultants? Pah! Only governments can afford to waste our millions on "feasability studies"!
Sound "Reinforcement" or Public Address? Make your mind up, two very different things.
"We definately don't need to be going down the route of line arrays," Preeecisely what you DO need IMHO! K.I.S.S. A good line source cab front and centre over the Prosc' arch is the best solution, unless the laws of physics have changed in the last 40years? Having two cabs is a result of a portable system and modern "fashion".
Then, you want peeps at the back of the hall to understand? What is on that wall at their backs? Just treating the slap coming off that could cost more than a modest PA rig!
Most of what a school "does" is speech based* so I am with whoever said get a decent SR system installed then hire, beg, borrow or di-da the heavy stuff.
*HAS been a while since I went tho'but!