A second vote for background
Evocation is now one of the weakest schools. The low-level evos are the best area effect spells for damage, but conjuration is steadily taking over. The orbs (and the fire-effect Cone of Cold) from Complete Arcane are conjuration, as are Glitterdust, Web, and Grease. About the only unmatched evocation left is Contingency, which is just golden. On the other hand, Evo has Fireball. Mmmm fireball.
Also, as a note, if your GM ups monter hit points for any reason, your evocations just got a _lot_ weaker and your save-or-dies didn't. We found this out the hard way. Sigh.
Illusion is generally handy, but depending on the group and GM can range from "I'm invisible" to "I make an illusion of a wall and hide the players behind it". It's very GM-call-dependent. YMMV.
Enchantment is chock-full of will-based Save or Dies, which overlaps with Necromancy.
Abjuration has Dispel Magic. Never, ever, ever, EVER give up dispel magic. It's a weak school (tell that to my Initiate of the Seven Veils, Greater Spell Focus [abjuration]), but Dispel Magic is critical. Also has Dismissal, and CA has Reciprocal Gyre which is just fun.
Transmutation... yeah, don't give this one up. Disintegrate, stat boosters, polymorph. Yeah.
As a final note. Necromancy has some _good_ spells. Check out the Book of Vile Darkness if you can (Lahm's Finger Darts) or Frostburn (there's a 2-3rd level dex damage spell). Ray of Enfeeblement is nice, but monsters get more strength as they get bigger. Now, what goes down with size? Right, dexterity. If you can start doing ~10 points of Dex damage per spell, you can take out dragons.