Necromancy, as a class of spells, already is "neutral". The playtest pack has eighteen spells with the label "necromancy". One of these (only) is marked as evil when used in excess (Animate Dead).
For the class of spells, there is no necessarily evil association that so many are suggesting. Which should mean that one can specialize as a Necromancer (a specialist in spells from the necromancy school) without being evil.
The alternative is that all spells so labeled should be marked as non-good. But they aren't. (I'll admit that would be interesting, and comes close to the world suggested in Revenge of the Sith).
To single out one spell seems to me a needless complication. Even with that complication, however, there is no reason why a good mage might not specialize in the school (and possibly choose not to take the one spell that is causing problems).
This is an issue with the sacred cow of calling that school of spells 'necromancy'. Because we are talking about two different issues here:
First, there is the subset of spells that deal with life and death energy-- innervation and degradation-- that were given the school identity of 'necromancy' way back when.
Second, there is the character concept of a 'Necromancer'-- someone who deals exclusively in the creation and the command of the Undead.
The problem here... is that life and death energy spells and the 'command of the Undead' are two separate things. And while the concept of a 'Necromancer' as we traditional know it (one who raises and commands the Undead) falls within the School of Necromancy (because those spells that animate and control the Undead are a small part of the circle of life and death energy spells)... one can use spells within the School of Necromancy and have nothing to do with dealing with the Undead.
By rights... the name of the school is wrong. The school should really be named something like Biomancy or Vitamancy... a name that evokes the feeling of life/death energy without tacking on the baggage of being a 'Necromancer'. If you are a Necromancer (as we all know it and identify it)... it's not that you just use a bunch of spells that fall within that school. It's that you deal with the Undead. So no... I don't think there's a need to catagorize all spells within the necromancy school as [evil]... because most of those spells have nothing to do with the power of the Necromancer.
I say we remove 'Necromancy' as the name of the school of spells... so that the name can be returned to the character concept of which we all identify. Because as many people rightly point out... clerics could/should/would be Necromancers too. So why pigeonhole it as purely a Wizardly thing?