As noted by others, it sounds as though you and your husband might benefit from a few sessions with a third party to talk through all these mindsets and philosophies re: education that are causing so much angst. I am troubled by your thought that 85% is failure. That said, that you two were not on the same page re: acceleration and he got the school to go ahead without discussing it with you speaks volumes which are very concerning. This alone seems likely to cause issues for your children. It would behoove you both to fix this situation.
On a side note, our son is in 7th grade (two grades acceleration) for math and language. The students are allowed to go back on certain assignments and revise their work for a partial grade increase (if done correctly the second time). I am a fan of this approach, because to simply grade and then penalize children (with a "bad" grade) at those ages does nothing except encourage perfectionism (imo). I think it far better to learn that writing is a process and to have a chance to understand what went awry, fix it and do better for the additional effort.
