This may be an especially interesting topic at this time when many schools in the USA are beginning the new school year, after a break for summer vacation, and families have a Back-To-School focus on streamlining for success.

When considering nutrition, type of physical activity, amount of sedentary time, and type of sedentary behavior... What to prioritize? What to let go?

The September 2023 e-newsletter of Neuroscience For Kids included raising awareness of recent research into various factors which correlate positively or negatively with a student's cognition, as measured by performance on a specific test:
Originally Posted by Sept 2023 Neuroscience For Kids e-newsletter
Elementary school children who eat a healthy diet show an increased time spent reading and have better reasoning skills

(Source: Naveed, S., et al., Effects of 2‐year dietary and physical activity intervention on cognition in children—a nonrandomized controlled trial. Scandinavian Journal of Medicine & Science in Sports, 2023; DOI: 10.1111/sms.14464).
Link to referenced study - https://onlinelibrary.wiley.com/doi/10.1111/sms.14464
- - Authors: Sehrish Naveed, Taisa Sallinen, Aino-Maija Eloranta, Hannamari Skog, Henna Jalkanen, Soren Brage, Ulf Ekelund,
- - Heikki Pentikäinen, Kai Savonen, Timo A. Lakka, Eero A. Haapala
- - Open Access
- - Published: August 09, 2023
- - DOI: https://onlinelibrary.wiley.com/doi/10.1111/sms.14464
- - also - https://pubmed.ncbi.nlm.nih.gov/37555467/

Keeping in mind that correlation does not imply causation, IMO, this is a FASCINATING abstract.
As I did not correctly anticipate the manner of each correlation, I went back and re-read.

Over the 2-year period of the study, which of these do you believe were found to correlate positively with increased cognition?
Which were found to correlate negatively with cognition?
Which had neither a positive or negative correlation?
1. Intervention of six dietary counseling sessions of 30-45 min
2. Intervention of six physical activity counseling sessions of 30-45 min
3. Encouragement to participate in after-school exercise clubs
4. Increased Baltic Sea Diet Score (BSDS) as an indicator of diet quality
5. Increased consumption of low-fat milk
6. Decreased consumption of red meat and sausages
7. Increased organized sports
8. Unsupervised physical activity
9. Increased sedentary time
10. Sedentary behavior: reading
11. Sedentary behavior: computer use
12. Sedentary behavior: writing

Link to Neuroscience For Kids - https://faculty.washington.edu/chudler/neurok.html
Link to Neuroscience For Kids, about - https://faculty.washington.edu/chudler/whowe.html
Link to Neuroscience For Kids, e-newsletter signup - https://faculty.washington.edu/chudler/newslet.html