To subscribe to your child's band calendar, scroll down and find the appropriate band (your child will know if you're not sure) and click on the +GoogleCalendar link in the bottom-right corner. This will add all relevant events to your online calendar and will be automatically kept to date.
Directions to adding the calendar to your iPhone can be found here. Use the following URLs to add the correct calendar. Android users can find the appropriate calendar below and click on the +GoogleCalendar link in the bottom-right corner.
Wind Ensemble and Symphonic Band - https://calendar.google.com/calendar/embed?src=2eba79ad368e50c03a8a672a0871a8f56f67942cdc4796a814ffbaf89f35d3c1%40group.calendar.google.com&ctz=America%2FChicago
Beginner Band - https://calendar.google.com/calendar/embed?src=eb1051c08bf7fce6cb15f7244b3405bc544ae9d35ce130a7573ce0600b0837cf%40group.calendar.google.com&ctz=America%2FChicago