The DC Office of Planning forecasts that the child population (ages 0-17) will grow at a faster rate than the overall population between 2015 and 2020 (a 11% increase compared to an 8.8% increase, respectively). However, this rate of growth will decrease in later years. The Office of Planning estimates that children ages 0-17 will account for 18.4% of the total population in 2030 compared to 16.8% as of 2010.
The DC Office of Planning forecasts that the most substantial growth will occur in the elementary age category (ages 3-10) between 2015 and 2020 and then 2020 to 2025 (an increase of more than 9,000 and 6,500 children, respectively). The large increase in infants and toddlers (ages 0-2) that was experienced earlier in the decade tapers off between 2020 and 2025. Middle and high school aged children aren't estimated to start increasing until after 2020.
Sources: US Census Bureau and DC Office of Planning Forecasts