This article details evidence that children are at risk and can transmit SARS-COV-2: Med J Australia

This article by Zoe Hyde, published in the Medical Journal of Australia online on August 12, goes over all the studies that show children can easily catch COVID-19 and pass on the virus to others, especially adults. The article is well worth reading in full for all the references to studies that have been ignored by those who want to open schools for political reasons or just out of ignorance.
The evidence is clear that children were accidentally excluded from many prior studies because schools were closed. In China’s case, transmission was stopped before significant numbers of children were infected.
After schools opened in Israel, outbreaks rapidly ensued. In Chile, an outbreak popped up quickly when a private school opened. Even in the US, closure of schools was associated with a marked drop in disease incidence– with greatest effect in states which acted early when there were few cases.
The author points out that investigation of child cases has been poor, with inadequate testing for asymptomatic cases. The studies that looked for it found that there were many cases in children with no symptoms.
This paragraph from the article says it all:
Schools are clearly neither inherently safe nor unsafe. The risk associated with these settings depends on the level of community transmission, and it must be continuously evaluated. Schools must not remain open for face-to-face teaching in the setting of ongoing community transmission. In regions where community transmission is minimal, risk-reduction strategies must be implemented in schools as a matter of urgency. Comprehensive guidelines have been developed (summarised in Box 1),20 but at a minimum, interventions should include the wearing of face masks by staff and students, increasing ventilation and indoor air quality, and the regular disinfection of shared surfaces.
https://www.mja.com.au/journal/2020/covid-19-children-and-schools-overlooked-and-risk
Here are the recommendations (adapted from Box 1, from reference 20– this document):
Classrooms:
Students and staff should wear face masks
Wash hands frequently
Move class outdoors if possible and repurpose large unused spaces as temporary classrooms
Keep class groups as distinct and separate as possible
Regularly disinfect shared surfaces
Buildings:
Increase ventilation by bringing in more fresh outdoor air
Filter indoor air
Supplement with portable air cleaners
Use plexiglass as a physical barrier around desks
Improve toilet hygiene and keep toilet lids closed, especially when flushing
Activities:
Hold physical education classes outdoors
Replace high-risk activities (e.g., choir practice) with safer alternatives
Schedules:
Stagger school arrival and departure times and class transitions
Modify school start times to allow students who use public transport to avoid rush hour
Policies:
Form a COVID-19 response team and plan
Prioritize staying home when sick
Encourage viral testing any time someone has symptoms, even if mild
Support remote learning options
Protect high-risk students and staff
(source: Jones E, Young A, Clevenger K et al. “Healthy schools: risk reduction strategies for reopening schools.” Cambridge, Massachusetts: Harvard T. H. Chan School of Public Health Healthy Buildings Program, 2020.)