At FHS, we receive many invitations to summer schools abroad. The list we publish is not exhaustive. In some cases, the universities offer tuition fee reduction if you are from a partner university.
The updated offer can be found here (our Czech website, but most of the information are in English).
You can apply for financial support for summer schools through POINT (Support for Internationalization of Charles University).
The largest number of summer school invitations start to appear throughout February - May.