Throughout April, the city’s public charters, including Success Academy, the network I operate, will hold their annual lotteries to select who gets a seat. These are needed because city charter schools have far more applicants than available slots for kids. Last year, applications to the city’s public charter schools hit an all-time high. More than 79,600 families vied for fewer than 27,000 seats, leaving 52,000 kids on waiting lists. The solution? Use available space in public-school buildings to co-locate new public charters.