My old school gives alumni children priority for nursery. Do I really register her before she's one?

My school sent an alumni newsletter last week with a note that children of former students can register early for nursery, with 'priority consideration'. Registration is open now, with a fee, for children born in her year. She isn't one yet, and nursery is still well over a year away. I also don't know whether we will want that school at all; it is a long drive from Ameerpet. Is early registration like this worth doing just to keep the option, or does priority usually mean very little?