I didn't even notice the schools, but "poison is necromancy" makes perfect sense if you think of the schools as character themes rather than mechanical functions of spells. Does this spell feel appropriate to a necromancer? Then it goes in necromancy. Whether it specifically involves draining life energy or creating undead isn't the point.
5E already has some of this; notice how spells that cause fear are necromancy, even though their function would seem to put them in enchantment. Doing schools this way makes it easier to ensure that each school is viable as a specialty.
This does cause one issue, which is the need for a really excessive number of spells to fill out eight schools. If 1D&D is going this route, it would be well served by returning to the AD&D approach where one spell could fall under multiple schools.
5E already has some of this; notice how spells that cause fear are necromancy, even though their function would seem to put them in enchantment. Doing schools this way makes it easier to ensure that each school is viable as a specialty.
This does cause one issue, which is the need for a really excessive number of spells to fill out eight schools. If 1D&D is going this route, it would be well served by returning to the AD&D approach where one spell could fall under multiple schools.