Some private schools end in Year 8?

[KTYmom]

Hello there
I am looking for a place in private school at Cambridge for my Year 5 daughter and feel very curious why some private schools are end in year 8 which is the second years of KS3. such as King's college school, St John's and St Faith's. Then what will leavers do after year8? Applying and taking assessment again to gain a place from another school? What if the favorite school has no place at that time? totally No idea for the Year setting. Very much appreciate the ideas/thoughts from you if your kids are/were in schools that end in Year 8. Other parents' information all welcome! Thank you very much!

At DD’s School they go from 3-16 but they are broken down into
Pre prep
Prep
Middle school
Senior school
Dd is in y9 and is now part of the senior school. It’s a small school so no change in site but slightly different uniform rules and different pastoral staff for each stage

@NaughtToThreeSadOnions , tenorladybeaker ,sleepwhenidie, BoundByBriars, EvaHarknessRose, CarrotCakeMuffins, RockNRollNerd, ShalomJackie
and other warm hearted parents,

Thank you all so so so much!
From day one no idea and nervous mom to now full of information and not panic mom, I appreciate so much for your help!
Now my daughter has attended a few school assessments and the result will be shortly sent. Believe there will be a good news.

@mastertomsmum
not confused at all...your information is crystal clear.

@Hoppinggreen
Yes, for some schools go from 3-13, Year 5 which my daughter's in is middle school. year 7 and year 8 is senior school.