Brand new secondary.V. Old secondary both under the same Trust

[HateSummer]

We have a new secondary school opening in our city in 2019. My dd is in year 5 and we’re thinking of where to send her.

The new school is under the same trust as it’s sister school that is outstanding. There is also another secondary run by the same trust which is “good”.
The new school will be right next door to the outstanding school and will gradually fill the school year by year. So if dd went there, year 7 will be the only year group and then they will be the eldest each year they fill up.

Would you send your child to an established “good” school or a new one where there wouldn’t be any interaction with older school children?