Unfortunately not because the window is about a metre, maybe a bit more off the floor in my room. Even my dresser (tallest furniture in my room) only goes about 5cm above the window.

My main concern is that he may sneak into the back yard and come in through the window in his old bedroom. Not much I can do about that I don’t think. My main bedroom door should be safe though. The locksmith reinforced the lock and the thing the lock bolt goes into by upgrading to longer nails and installing a couple extra