Mixed students and groups always perform better
replies(1):
https://www.kidsnews.com.au/humanities/study-reveals-benefit...
Generally, in mixed-gender groups aged 13+, you will have some dating activity and a subsequent drama / bad blood from various heartbreaks and betrayals. Having to sit in the same classroom makes everything emotionally worse.
This is somewhat less of a problem if the same activites take place outside school and thus are less likely to complicate relationships within the class.