Verbal means nothing --- new coach or the one that gave it.
Hell even written ones can be withdrawn at any time, yes even after your child is attending the school.
If you sign a NLI then that cannot be changed at any time. It's good for the full year that it covers but NLI's only cover one year.
As you currenty see kids who were comitted to one school, comitting to another, in many cases that's due to the first coach saying we no longer want you or we are pushing you out a year. Happens all the time whether there is a coaching change or not.