Genes in Space is a national STEM competition freely accessible to students in grades 7-12. They have conducted missions on the ISS since 2015. Applications for the 2026 mission opened on January 5th and are due by April 10th. Besides the grand prize (your mission on the ISS), there are 25 other significant prizes.
Details and resources for teachers and students can be found in their website: https://www.genesinspace.org/