If you want to prevent a child from being able to open a window, then installing window latches is a good option. When selecting which type make sure that, while preventing a child from opening the window, it is still easy for an adult to do so.
Window guards are a good choice if you don’t want a child to have any access to a window. They are usually built with bars that will stop a child from reaching the window. Just make sure that the window guards you buy comply with all modern safety standards which include bars being spaced no more than 4 inches apart to prevent a child from getting their head or other body parts trapped.
Perhaps you still want to be able to open a window and at the same time childproof it. In this case, window stops would be the best choice. These will allow you to open the window to a set width, however, as is the case with window guards, do not set the opening to more than 4 inches.
Another simple way to prevent a child from accessing a window is by the positioning of furniture, keep any furniture a child can climb on away from windows. You also want to keep in mind that even if windows have screens in them, additional safety measures must be taken as they do not protect against a fall.