[WPOZZZ]

I need to change out some jalousie slats to make things a bit safer for my nephew. He is 18 months old and is at that ae where he plays with everything. I got some plexi and had it cut to size, but they are too flexible. He like to grab the jalousies and open and close the windows. He also likes to climb on the coffee table and stand up looking out the window.

Any suggestions? I could go with wooden slats as a last resort. I looked at corrugated plaskolite board, but unsure if it will be rigid enough.