Need Advice: New foster parent here

We have a fun situation. We basically became foster parents unexpectedly.... long story so sorry

My brother in law (16) moved to my state to get to know his bio father and little half-sister. He has been living with them for the past 2 months, we have him over on Sunday's for game night. His mother, my mother in law, lives across country in New York. Due to the distance we set up a durable power of attorney just in case, so my husband and I can act in MIL's place for school, medical etc.

Something happened late Sunday night and the kids were taken by CPS. By Monday afternoon we were given custody of BIL and his half sister.

So now I went from a FTM with an 8month old to having my baby, a 10yr old and 16 yr old. The kids seem to be handling it well. Now I have reached out to the schools to check grades. Little girl is doing great, straight A's no problems.

This is where I need help. BIL has been kicked out of every school within 2 hrs of moms home in NY. Sending him home would mean no chance of a HS diploma. So we made a deal, if he can get good grades and behave we will consider him staying with us for school. But He is disruptive in class, failing almost every class and so on. I have access to all his grades online now. I'm working with him to complete all past due work, even if he won't get credit, setting up tutors and where possible make up tests. I have no idea how to help him pay attention in class and reduce talking/disrupting class. He doesn't have anything really, some clothes and his school things, nothing I can take away as punishment. He has no friends in the area, grounding won't work... Any ideas?

I'm honestly hoping structure and proper breakfast and dinner will make a difference...