Are we doing the right thing? please help

[hopeful_25]

My 12yo ss is failing 6th grade.  Since dh and I have been married for 8yrs, we have always had him during the week.  BM recently remarried (saying she never would to ss after last husband passed) and they built a new house to include new husband's kids.  Ss says he wants to live here in the next school year, but bm refuses to let him so he gave up on school.  Everyone is so frustrated that he won't do homework we have been trying to think of ways to help.  We have him eow and two overnights during the week now but dh decided to have him stay at bm during the week all through Feb.  We get him every weekend.  Since dh told her about it, she has really stepped up to the plate in helping him with homework which is great!  Counselor said that if his grades come up then we should go back to the old schedule.  If not he will stay at bm's house another month on this new schedule.  SS now thinks we don't want him here and he hates the idea of not coming during the week.  We have explained that we do want him here but he cannot be failing school.  My fear is that it will all back-fire on us even though we feel it is in the best interest of the child.  I am afraid that when we do try to have him come here next year like he wants she will say that he did much better at her house with the new schedule.  New SD and ss do not get along so he wants to be here.  I don't want to go to court over it but she says he is such a punk and alot of times she calls asking dh what she should do with him.  She has an alarm system on his window and video monitoring facing the doorway (door removed).  She keeps mentioning military school.  Why not try our house first?  That is what dh keeps telling her.  Do you think it will all back-fire or give it a whirl?  Thanks for any help or advice--it has been making me sick to my stomach thinking we are making a mistake and should abandon this new schedule.  Are we letting ss down in some way?  Are we really helping him or telling him he is not good enough?