Window locks for toddlers?

[Nissykins2]

Historically, at this time of year, I turn off the heat/AC and throw open the windows. We're on the third floor, though, and I've got a shelf under my 2-year-old son's window that basically acts as a window seat. I am not comfortable leaving his window open while he's unsupervised, but am afraid his room will be stuffy overnight with the windows closed. I have read reviews of several window locks, and every one seems to mention at least one kid who figured out how to disable it. Have any of you found a good solution to the problem of keeping upstairs windows safe for little ones?  Thanks!

[La Bibliotecaria Feroz]

Can't you just open the top sash instead of the bottom one? You would probably still want to use some kind of guard, but it seems like that would make it much harder to defeat.

My three-year-old can now UNLOCK his window. But we are moving in a few weeks and hopefully the new place will not have such easily accessed windows.

[zolotiyeruki]

Can you put a screw in the window slide that prevents the window from opening more than X inches?

[MicroRN]

Do you want to lock it closed or do you want to be able to leave it open?

Guardian Angel Window Guards work really well.  Expensive, but worth it.  We live in a 1940's house and the window screen pop out of the frame with very little pressure.   

[Nissykins2]

Thanks for the responses, guys!  Our windows only open from the bottom, and I worry about adding something like a screw in case of a fire. I will look into the Guardian Angel Window Guards.

[agent_clone]

Assuming the windows slide up and down would you want something similar to these? http://www.ebay.co.uk/itm/Delf-Window-Sash-Stop-0716PB-Weeks-Polished-Brass-/251262973232

I would assume the trick is to put it at a height that the toddler can't reach, which assuming the windows start around 1m (a bit over 3ft) from the floor should be doable so long as they aren't moving chairs around.

I know my parents windows have little latch things that you can move in and out to allow for the window to be stopped at a certain point, or allow it to be opened more (like what I think these things are doing).

[Rebecca Stapler]

We have these window guards: http://www.amazon.com/gp/product/B000H4C6NI/ref=as_li_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B000H4C6NI&linkCode=as2&tag=stapleconfes-20&linkId=5AAQ64554ZMRHUPH.

We paid $50 each for them, though, so IDK why they're so expensive now. But they have clips so you can easily undo them in case of fire. We have two big windows that open and a window seat in front of them (where my little guy plays a lot), so this is the only thing that we felt safe using.