If I live far away from the high school will that decrease my chance at custody? How?

I think you are talking about placement, rather than custody, which are not the same thing. Consulting a skilled family law attorney would be a good idea. The 45-minute trip twice a day is likely to weigh in favor of the other parent. But a lawyer would be able to tease out additional facts and circumstances which might help our case. It's almost always worth the investment. Good Luck.

No, this shouldn't be a factor in custody. The child can always be transferred to a high school closer to where you presently live. The courts look at other issues regarding what is in the best interest of the child to determine custody.

It could be a factor that a Judge would consider, but I would not expect it to be something that any Court places much weight on when making a decision. Far more important are the relationship the child has with each parent, whether there are any substance abuse or mental health concerns with either parent, the track record of each parent with regards to co-parenting and communications, and what the status quo has been up to this point (who has been the primary custodian in the 12-24 months prior to the custody hearing).

I think the issue would only arise if this is a public school and you have moved out of her school district. Residence can make all the difference as to whether she has to change schools or not which the court may or may not see as being in her best interest.

That should not be the deciding factor.