Installing window latches is a good way of preventing a child from being able to open a window. It's also important that you choose latches that are easy for adults to open as well as stopping a child from doing so.
To prevent a child from gaining access to the window at all, window guards are a good option. These are normally built with bars designed to stop the child. While all new window guards should meet the correct safety standards, it is still a good idea to check that the bars are spaced no more than 4 inches apart. Any more than this and a child could get their head, or another body part trapped.
If you still want to open the window but only to a certain width, then window stops are a good choice. As mentioned, do not set the window opening to more than 4 inches.
Another way you can help to childproof your home is by positioning furniture away from windows. Its also important to keep in mind that even if a window has a screen in it, this will not provide any protection against a fall so, additional safety measures will still need to be taken.