Splitting room - hardboard ceiling?

[Beansandcheesearegood]

My 2 children ds 7 abd dd10 share a room. Not ideal but reality for now. Dd has a high sleeper that we've hard boarded up the bit under the bed so it's a bit of a room divide and she has this private area but she still wants more privacy. I'm thinking of trying to put a board from top of bed to ceiling and attach it. Any advice how to do it? Anyone done similar?

I found this a while ago, which I think is brilliant and gives lots of privacy:

But if I were to use hardboard, I would attach battening to walls and ceiling and screw it to those.
B&Q also sell boards for room division.

L brackets? I think you’d have to screw a batten into the ceiling joists first though then attach the l brackets to that then to the board.