Is class 9 too late to move from CBSE to ICSE? Thinking of St. Patrick's in Secunderabad

We have been talking at home about moving closer to the Secunderabad side, possibly within the year, and St. Patrick's High School came up as one of the schools nearby. Our son has just finished class 8 in a CBSE school in Miyapur. My worry is timing. The ICSE board exam is at the end of class 10, so a move now gives him barely a year to settle into a new syllabus, new books and a different way of writing answers. Not moving him means either staying put for two more years or a very long commute if we do shift. For anyone whose child switched boards at class 9: how did it go? And does anyone know whether St. Patrick's takes joiners in class 9 at all?