Alas, my windows are swing-open jobs with screens attached on the outside. The particular one that was broken in had a teensy little latch at the bottom but otherwise was two windows that swing open like this: \__/ The bottom latch was mostly loose, so the guy removed the outer screen, then basically pushed really hard until the bottom and center latches gave way.

There's not a really easy way to block them up, so what we did was add an additional latch hooking them together more tightly, and wire through the top curtain area to tie it shut, and the landlords have a contractor in to provide a more permanent and pleasant solution.