Yes, absolutely! The admissions is on a rolling basis. No, there is no deadline for application. When it's full then they will not take any more students. Most students will apply before December for the next summer.
If you are going to be there late, you should write to Ethan Shapiro, who is the Director of Summer School, to ask him.
If your child is going to be late and if it affects his/her grades, that may not be that good.
