DOB already has a date picker when editing user contact cards - it would make sense to apply that everywhere. It's also more convenient for parents filling out applications.
Similar to this idea re: Inquiry forms:
https://blackbaudk12.ideas.aha.io/ideas/K12OB-I-881
Instead of a date picker, I would suggest a date dropdown options for month, day, and year for digital accessibility purposes. The date picker is hard for screen readers programs and those relying solely on keyboard navigation to appropriately navigate the calendar feature.