Divide the site into two parts, and sell off the part with the nice views to developers. Then build the new high school with more stories and parking in the back (and remove the useless grassy yard). I heard they had a ridiculously high offer for the site, and I'm sure they could still make a lot of money by just selling part of the site. This plan would still allow them to keep the high school where they want it, while also making some money for new textbooks/computers/etc which could benefit the whole school system. This would also create a denser, more urban environment with no setbacks from the sidewalk, which would be a much better fit for a neighborhood that's so close to downtown.
I also think the simultaneous development of a new high school AND a new residential/retail development could be the shot in the arm this stretch of Detroit needs. There are plenty of empty/underutilized properties directly adjacent to this site. Has CMSD even thought of this? I can't think of any negatives to this solution. It allows the school to be built there, as well as new (potentially mixed-use) development next-door, and is overall a more efficient use of land.