It is easy to fill the summer months if you are willing to take school age kids who of course are also out of school. Problem is you will end up with kids not used to being with little ones all day and expecting to go on outings, the park, be outside etc all day and that doesn't fit with infant nap schedules.

What I do with teachers is charge them more during the school year ($200 week including Christmas and March breaks instead of the regular $185) but then let them have the summer off with the privelege of bringing the child one day a week (day of my choice). They also pay for the first two weeks of Sept before they leave in June. Then if they dont' return it is a lost deposit. What this does is also prevent the teacher that says they will leave the child for the summer and then come June change their minds (or tell you the truth which is they never intended child to stay). Also charging more during the year works better as some teachers are paid only for the 10 months but make extra as in their summer pay is spread out whereas some school boards pay 12 times and the teachers get a pay in the summer.

For a teacher that insists no way are they paying then they are given a Sept to June contract at my regular rates, have to pay for Christmas and March breaks but can also send child if they want some catch up around the house time. But I make it clear that I will then start to advertise to fill an opening for July. They may luck out and find that I have a child leaving over the summer to start school and be able to have that space the following Sept but of course that is never a sure thing.

It comes down to the teacher not being able to have everything they want. They want the security of their child having the same daycare provider throughout preschool but not willing to pay for it.