Do you mean they are on a fixed term contract? Generally fixed term should be until 31 August and you would need to consider why it was temporary until just the end of term. Their contract letter should have officially stated an end date and a reason why.

It depends on their contract. Where I work now, holiday pay is based on weeks worked in an academic year. If someone joins the academy on 1st September and they work until the last day of the summer term, they are paid until 31st August. However, if they started in January they would not receive the full entitlement of the summer holidays. They would receive a proportion.

When I worked for a maintained school we paid until the end of the summer holidays regardless of start date, if the employee worked up until the last day of term.