Less than 30 minutes' drive from the hip tech hub of Tel Aviv, Bnei Brak feels like another country and another time. Men scurry into synagogues and seminaries to study the Torah — the Jewish holy text — while kids push other children in prams, without a smartphone in sight. The ultra-Orthodox city is Israel's most densely populated, its streets straining under the weight of the community's sky-high birthrate. There's also a staggeringly high unemployment rate. Almost half of ultra-Orthodox men don't work because they're studying the Torah at a huge cost to the state. Children freely play in the...