Escuela concertada -kindergarten (Barcelona)

Any experience with "escuelas concertadas?" They are the "private" schools subsidized by the govt. We live in the Eixample area and although our child is an "excellent candidate" for the private schools in Zona Alta, we are wait listed and worried.
Any advice would be welcome.
Also, if there are any families with Kindergarten-aged children, I'd love to participate in a park day!