Help to place our child in the same school as his sibling

Our son dylan Wallace is currently In carlibar primary school where he has made friends learned alot, and has grown alot as an individual now that he is in the last year of primary and getting ready to start the next chapter in his life and go into high school which is  very scarey at the best of times, but it's even more scary and stressful when you are told that there is no room for one child in there school, We are devastated as is our son. We understand these things do happen but to be told after our son has been looking forward to it that there is NO room is, heartwrenching, so we are now turning to this to see if we can get as much feed back and signatures as we can to take forward to the education board to show them that we desperately want our son to get into barrhead high school.