School outdoor spaces provide many mental and physical benefits for students. Yet, teachers may not have the opportunity to conduct lessons in these outdoor spaces due to personal or systemic barriers. While K-8 teachers' perceptions of barriers have been well explored, there is currently a lack of research investigating high school teachers' perceptions. This study used an online survey to explore the barriers and strategies of 154 high school teachers in using their schools' outdoor spaces. These results showed that there were differences between barriers from previous studies that could affect how high school teachers overcome them. Knowing these barriers and some strategies teachers have used to overcome them can play a major role in increasing the use of school outdoor spaces to meet the needs of today's high school students.