Is this Tune Mun the placement of SJS? I think this year is very abnormal because of the overwhelming demand, so kids from TKO also send to KJS or SJS. I guess you should ask if the school has special bus arrangement for these cases, though it may be tough. Has SJS held parents orientation already?
I m not sure, but last time when I was SJS, I saw school bus to Yuen Long, so why not Tuen Mun. Pls check SJS, they might refer you to the bus company.
Just call SJS and ask tomorrow, the easiest way. This coming year may be so different so hope the school can have some special arrangement for some kids which is not in their placement zone.