The story around Bloom's two sigma is a bit complex https://nintil.com/bloom-sigma/

Thank you for this and for parent’s comment - I know what rabbit hole I’m going down today.

	▲	Herring an hour ago \| parent [-]
		Hmm, it might be better to just go straight to what leading countries currently do (Finland/Estonia/Japan/Singapore/etc). Other factors probably play a bigger role, like school funding, school autonomy, teacher professionalism (high education level + continuing education + good pay), free school meals/healthcare/transportation etc