Kate Gentles is right to be surprised that 'educational use' is permitted
under US copyright law without permission. One can use certain materials
for 'educational use' without obtaining permission, but the conditions
are spelled out fairly clearly in the 'fair use' provisions of the US
Copyright Law. In general excerpts of a work may be reproduced under
certain circumstances, but reproduction of a complete work is not
allowed. Thus, for images (such as clip art) reproduction cannot usually
be assumed to be permitted.
In many cases where no profit is to be made from the use permission is
granted without any fee, but this does not remove the requirement to make
P.S. I am not a lawyer, but a retired librarian.