This paper explores the views of leading Czech physicists regarding a physics curriculum for upper secondary schools. This paper presents the first part of an effort to define starting points for a new physics curriculum in Czechia (subsequent phases would analyze the opinions of other scientists, education experts, and physics teachers regarding the physicists' ideas) and create a new physics textbook for upper secondary schools. The methodology was inspired especially by the objectivist grounded theory. We conducted in-depth interviews about the upper secondary physics curriculum with 29 leading Czech physicists and identified 56 ideas (categories) that they agreed on (according to the interview analysis). Subsequently, a questionnaire was created based on these 56 ideas. Two years later, the same group of physicists were asked to express their opinions on the ideas on a 7-point Likert scale. The new survey sought to clarify the relevance and permanence of the ideas, and the physicists' willingness to collaborate on constructing a physics curriculum for upper secondary schools. Four core categories--students, physics, context, and math--were identified through a comparison of the relevance of the ideas. Additionally, we compared the questionnaire answers of a physicist with their opinions during the interview and identified 43 ideas as permanent (in the 2-year interval). Surprisingly, 26 of the 29 researchers in the initial study completed the subsequent questionnaire survey and 13 among these expressed their willingness to contribute to the development of a physics textbook for upper secondary schools.