We only offer an annual subscription for the EDU licence. This has been done for a variety of reasons, such as:
We want to encourage the use of AppShed across the whole school, and for a variety of subjects. The annual licence gives the school time to use it in a greater variety of ways.
We have tried to keep the cost as low as possible. Reducing the amount of admin our staff have to do (handling monthly invoices, payments, statements etc) helps us to be more efficient.
Monthly fees would be more expensive for schools. We take into account that schools are not uniformly active over a 12 month period, so the monthly fee would be much higher than 1/12 the annual fee.
Hopefully you will find the the EDU licence offers great value for money, and enables your school to incorporate app building across the whole school, in a variety of subjects.