Not surprising, because they don't address the fundamental issues. Why would mindfulness help with depression, better than teaching these kids how to grieve in an effective, healthy way?
CBT can be helpful, but it 'intellectualizes' problems too much. How about teaching these kids how to increase their self-confidence? How to identify their emotional needs? How to build their social skills, resolve conflicts in relationships, and assert their personal boundaries? Most sure aren't learning that from their parents.
These interventions are far too superficial to obtain the intended results. I'll be pointlessly provocative now: they almost seem intended so that teachers/interveners can avoid having to deal head-on, one-on-one, with their students' "messy" emotions. No need for school adults to have empathic, difficult conversations with kids whose parents are undergoing a divorce. Instead, just teach the kids (as a group) how to intellectualize their emotions, or distance themselves from them. It minimizes the role of teachers and other trusted adults as a social support system, it places the onus on kids to "fix themselves", and it downplays the importance of emotions in causing these problems in the first place. It makes things very impersonal. Imagine if sex-ed classes were founded on Victorian notions of decency, would they be of any help? It concerns me that so many intelligent, thoughtful scientists are barking up the wrong trees. If they refocused their efforts, they could be far more effective.