ESTA vs Visa for International Attendees:
Students traveling to the United States, from a Visa Waiver Program (VWP) country, have the option to apply for an Electronic System for Travel Authorization (ESTA). It is an extremly easy and cheap alternative to a standard visa and is valid for travels for up to 90 days including vacation and business trips. An ESTA is not valid to attend a school, i.e., be a student in the US.
If you are traveling with an ESTA, please ask Daphne Klemme for an acceptance letter tailored to ESTA, where BSS will be referred to as simply “BSS conference” and “BSS workshop”, i.e., no “school” will be mentioned to avoid any conflict and/or confusion.
Students coming from countries not covered by the VWP should apply for a standard Business (B-1) visa which permits attending a scientific, educational, professional, or business convention or conference. If in doubt, check with the U.S. Department of State - Bureau of Consular Affairs, for further information.