I agree. And window locks operable by the tenant would be a good idea.
Ensure the windows work properly (ie both halves of the sash open), then the parents can control which bit's open. Any open window can be a danger if the child is very inquisitive - the parents have to be responsible and not leave the kid alone in a room with open windows if there's any danger of them falling out, or fit window bars etc.
I have dreamed in my life, dreams that have stayed with me ever after, and changed my ideas; they have gone through and through me, like wine through water, and altered the colour of my mind. Emily Bronte