initial period for ast

Tenancy Types and Management

we rent to students on a 10 month initial contract. One of the students has left the property and gone back home as he is unwell.we were informed of this formally about a month ago. we were under the impression that having signed the tenancy agreement for 10 months he was liable for this period, however i was recently told that legally we can only keep the student to the contract for six months and that after this period he can give notice to quit which effectively he has done. who is right?