This error occurs when your school type is not present on your school table - if you go to Admin>Config>Core Set Up and check the below:-
School Type must be within the following valid values and ranges for <Phase>:
'NS' equal ['49', '50', '51']
'PS' equals ['01'-'04', '16'-'18', '42','43' and '49']
'MP' equals ['05'-'06', '45' and '49']
'MS' equal ['07', '08', '41' and '49']
'SS' equals ['09'-'12', '21', '22', '25'-'33', '36'-'39', '44', '46'-'49']
'SP' equals ['49', '52' and '53']
'PR' equals ['49' and '54']
'AT' equals ['49' and '55']
School Type must NOT be '50', '51', '52', '53', or '54' for <Phase> equals 'AT'