Checkbox Array Value Saved To DB

Being a novice to this topic, I would like to ask how to save the results of a checkbox group as an array, and then afterward save the array to a database when the form is submitted.

Here’s a screenshot image of the form’s checkbox group:

Checkbox1 value = Board, Checkbox2 value = Day, Checkbox3 value = Night. Whatever is checked would be saved as a comma separated value to the School Type column of the database.

Any help is very appreciated. Thank you for your consideration.