Curtains letting light in round the sides!

[Berangere]

Just moved house, we have thick Roman blinds in DS’s room but a small gap down the sides of them. We’ve put up some John Lewis lined curtains as well as the blinds, and there’s still strips of light either side of the curtains when they’re drawn. DS is nearly 1 and sleeps better when the room is darker. Currently propping up picture frames etc to hold the curtains down!
Is there anything I can do to remedy this?

I masking tape mine to the wall but they're on poles and are only cheap ikea ones. Going to switch to a track which will work better.

You could use sticky back velcro? One bit inside the curtains and one bit on the wall?

Curtains should have a return at the outside edges so you can hook the curtain hook that’s nearest the edge of the curtain to a hook that you place at the same height as the track but on the wall.
So the curtain edge sort of bends round and the light is excluded. Don’t know if that makes any sense!

I just quickly googled and there’s a demo of what to do on this website
https://www.addicted2decorating.com/how-to-hang-draperies-and-curtains-like-a-designer.html

That's genius!

Can't remember which hotel it was but they have a frame and the side of the curtain velcros to it. It was brilliant at blocking out the light