Invention rights vest first in the inventor(s). Intellectual property rights can only be conveyed by a signed writing. If you are paid to create something, shop rights in the patent could be obtained by the entity paying you. If the school was not paying you and you did not sign an agreement to convey patent rights, I cannot think of any other means by which your invention rights could become the property of the school.
If it is a public school, the school is treated as a part of the government and is held to a higher standard under the Constitution to prevent government taking from private citizens. There may be additional facts that create an ownership dispute, but nothing in your details suggests the school has accrued any intellectual property rights in your project.
Answered on Mar 25th, 2014 at 4:13 PM