Necromantic Healer

Their healing spells don't show much effect on living creatures, but show startling effects on the recently deceased

Cursed Healing

As the wielder only believes themselves a healer, the spells they cast show some oddities.

When casting a healing spell on a living creature it only restores half the rolled number of hit points, and full rolled hit points on undead

When cast on a deceased creature, if the creature died within the last 24 hours it is resurrected as a [monster]zombie[/spell] but with all its original stats 

Zombies raised this way are under the effect of Charm Person indefinitely, until caster does anything harmful to the creature

Necromancy Savant

Beginning when you select this school at 2nd level, the gold and time you must spend to copy a necromancy spell into your spellbook is halved. You also gain access to spells from the cleric spell list, but the gold and time required to copy a cleric spell into your spellbook is doubled.

Grim Harvest

At 2nd level, you gain the ability to reap life energy from creatures you kill with your spells. Once per turn when you kill one or more creatures with a spell of 1st level or higher, you regain hit points equal to twice the spell’s level, or three times its level if the spell belongs to the School of Necromancy. You don’t gain this benefit for killing constructs or undead.

Resurrector

Beginning at 2nd level, whenever you raise a zombie through the use of a healing spell,  but not the Cursed Healing spell, regain hitpoints equal to the spells level and recover up to half the spell level rounded down (min 1) usages of Cursed Healing spell

Undead Thralls

At 5th level, you add the animate dead spell to your spellbook if it is not there already. When you cast animate dead, you can target one additional corpse or pile of bones, creating another zombie or skeleton, as appropriate.

Whenever you create an undead using a necromancy spell, it has additional benefits:

• The creature’s hit point maximum is increased by an amount equal to your wizard level.
• The creature adds your proficiency bonus to its weapon damage rolls.

Exsanguinated Resurrector

Beginning at 6th level, you have spent so much time benefiting from the undead you raise, you have worked out a means to benefit your undead instead.

Instead of regaining hitpoints and usages of Cursed Healing spell when raising an undead through the use of healing spells you can add a bonus to one of the creatures ability scores equal to half the spells level rounded down (min 1). The increased ability score cannot be raised above 20.

Inured to Undeath

Beginning at 10th level, you have resistance to necrotic damage, and your hit point maximum can’t be reduced. You have spent so much time dealing with undead and the forces that animate them that you have become inured to some of their worst effects.

Command Undead

Starting at 14th level, you can use magic to bring undead under your control, even those created by other wizards. As an action, you can choose one undead that you can see within 60 feet of you. That creature must make a Charisma saving throw against your wizard spell save DC. If it succeeds, you can’t use this feature on it again. If it fails, it becomes friendly to you and obeys your commands until you use this feature again.

Intelligent undead are harder to control in this way. If the target has an Intelligence of 8 or higher, it has advantage on the saving throw. If it fails the saving throw and has an Intelligence of 12 or higher, it can repeat the saving throw at the end of every hour until it succeeds and breaks free.