My kids are/will attend a high school with none of their friends. We chose an Agricultural boarding high school for our kids and they won't have any of their friends attending there. Also, because of the nature of the school, though they will be there together, they will really have limited time where they actually spend time together anyway and only if they choose to hang out with each other. I don't think having kids attend the same school is a deal breaker for that reason, but in terms of logistics it might make a difference if that makes sense? You've got 3 kids and you could possibly have them at 3 different schools. It can be hard to keep up with everything the schools have going on - we find it hard at times and one of them is a boarding school so it's not like we're even able to be there everyday. But what it comes down to is picking the best school for your child. If that means that they will not be there together or all be at the same school, then that's just the way it has to be. I'm guessing it's not a boarding school? And if that's the case, then it might be better for them in terms of their relationship with each other if they aren't at the same school/there together because it gives them a break from each other and they don't take their siblings for granted, if that makes sense?