My dd homeschooled her whole life and started public school for high school. We are in Johnston County and it has been a great experience. We moved from Raleigh and have about 10 acres. Things can be confusing but here is some help:
West Johnston High - good school, large, good sports, great band program. The addresses that feed into it is confusing because it pulls from a community that is unincorporated but locals call it Cleveland or 40/42. It is not located near these towns but the addresses will be: Benson,Willow Springs, Angier, and Garner. ( most of these towns straddle multiple counties so it would be in the Johnston County section.
Cleveland High-this is the same area as West. Brand new school and is smaller with a great community feel to it. Cant say a negative about it! Again, it is in unincorporated area so addresses are really odd and aren't in these actual towns. You will see mostly Garner, Clayton, and a small section with a Smithfield address.
Wake Christian- we have lots of friends there as well. You will see kids from Raleigh, Cary, all over the Johnston County and Harnett County
Good luck. We really like our community. Feel free to PM me if I can help any further.