No, schema not supported, but you can create many databases files. Here manual for create database with Firebird tool. Also you can create database with IBExpert or similar tool.
Also, you can create sql-cript for automate it:
$ isql -q -i create-db.sql
Also you can run it from java code.
--Contents of create-db.sql
CREATE DATABASE '/my/path/my-db.fdb' page_size 8192 USER 'SYSDBA' PASSWORD 'masterkey';
CREATE EXCEPTION EX_SOME_EXCEPTION 'Some extension message';
CREATE TABLE ROOMS (
ID integer NOT NULL PRIMARY KEY,
Number char(10),
Name char(100),
Network char(100),
Memo char(100)
);
CREATE GENERATOR ROOMS_IDGEN;
SET TERM !! ;
CREATE TRIGGER ON_ROOMS_INS FOR ROOMS BEFORE INSERT AS
BEGIN
IF (NEW.ID IS NULL) THEN NEW.ID=GEN_ID(ROOMS_IDGEN, 1);
END !!
SET TERM ; !!
....