I absolutely would love Boarding Schools back. The Sims 2 and 3 had this and it was great. The different kinds of Private Schools had different uniform colors to coincide and they were really cute.
I added this to my list when commenting on Keekee53's request for more High End things for Sims to spend their money on. The link for the original post is here if you want to check out her request. My response is lengthy but here is the excerpt pertaining to schools.
https://forums.thesims.com/en_US/discussion/980181/high-end-stuff-pack-more-expensive-items/p1
10.
Private School - K-12, You have to pay tuition, Uniforms, Themed type School, Bonus to certain Skills and unique objects appropriate to the type of school.
Sims 3 had a list of Boarding Schools
- Fort Starch Military School - §800
- School of Peace & Love - §800
- Dribbledine Sports Academy - §1,200
- LeFromage Art School - §1,200
- Smuggsworth Prep School - §1,600
Sims 2 & 3 had themhttp://thumbs2.modthesims.info/img/1/0/5/2/6/7/5/MTS_Phaenoh-661841-PrivateSchoolGirls.jpg
http://static.independent.co.uk/s3fs-public/thumbnails/image/2014/07/02/22/v2-web-private-schools-getty.jpg
https://sc01.alicdn.com/kf/HTB11zQUJFXXXXceXXXXq6xXFXXXU/221122829/HTB11zQUJFXXXXceXXXXq6xXFXXXU.jpg
https://www.clipartkey.com/mpngs/m/92-921816_new-school-uniform-private-school-uniforms-purple.png
Military School - Fort Starch Military School was the Military School in Sims 3
http://i.dailymail.co.uk/i/pix/2016/05/11/06/34078D8600000578-3582969-image-a-1_1462945760798.jpg
http://photos1.blogger.com/blogger/3963/613/1600/2006%200425%20Wayne%2C%20PA%20Valley%20Forge%20Military%20Academy%20048.jpg