If you delete your list, it's gone from within MailChimp. To re-add your list, you would need to contact S.D. Professionals, LLC at firstname.lastname@example.org.
The minimum cost to reconnect your BOS to your existing MailChimp account is $350. and only parents of currently active children will be re-added (If you had email addresses of parents whose kids had already graduated, they will no longer exist when your list is reconnected).