This randomized control trial found that weekly home visits and mother-child group sessions, both of which included nutritional education, had an equal effect on cognition and language. Because of their lower per-child cost, group sessions are more scalable than home visits. This article is behind a paywall.
Grantham-McGregor, Sally, Akanksha Adya, Orazio Attanasio, et al. Pediatrics, December 2020