Is this a feasible journey for an 11 year old? Are there any buses or coaches which go directly would anyone know?

Looking at google/ Apple maps, it is currently a 50 minute drive. I would guess it’s even more at school arrival times and public transport looks to be even longer with at least a couple of changes.

Might be worth you trying the journey yourself at the appropriate time of day to see how it works out, but my view would be no, it’s not feasible.

I occasionally do a similar (but easier) journey. In my opinion it isn't feasible for a child/teenager for 7 years. I dread it each time I do it (about once a month).

I would suggest using Google to see how long it takes door-to-door.

Although UGS doesn't seem to list anything about transport St Bernard's do have the following and I know that the 2 schools share some of the coach providers http://www.st-bernards.slough.sch.uk/373/transport

Personally I would suggest looking at your local secondary schools instead of making your child travel so far. Travel wise you just need poor weather, an accident etc and then your DC is stuck.

Good luck btw

More info as I can't edit my post lol.

The transport info on the 2019 Admissions page for St Bernard's is a bit different and mentions a coach from Harrow.
Again cos it is for a different school you might want to check if they take kids from Upton. But looking at Moovit, your child would be looking at an easy 80 min journey using public transport and that is assuming little traffic and no problems with the weather (buses 140 and then 81).

So your best options are either move closer if your DC has a place at Upton or look at local schools/ easier to get to taking into account the tube system (ie Bakerloo/ Metroplitan lines).