Cars at school pick up and drop off times are parking on the fields causing issues

Cars on the school run are parking on the field on Fairfield’s estate causing issues with tyre marks and mud. The grass is slowly disappearing and is very boggy and muddy. The residents aren’t happy as we have been complaining for months without any avail. We only have this field left to play on or walk our dogs and it’s being destroyed by 40 odd cars that park on this piece of green in the week days. Please can something be done by erecting wooden barriers or something similar so cars can’t keep parking here. It’s so busy and it’s driving us mad