Hi and welcome to the Forum.
Schools - apart from the fact we speak the same language (and even that is sometimes frustrating), there really is no comparison between the US and UK school system; we don't salute the flag, nor do we sing the national anthem at the start of the school day. My concern would be your 12 year old as he would be returning to the US at age 15/16 with no preparation to continue in the US and be completely out of the loop for further education back home.
For your other questions:
Some kids walk to school, others get dropped off by family, others take the bus. Our kids walked, the school was across the road from our house.
When I came back to London from the US as a child many years ago I didn't experience any issues with my talking like a Kentucky hillbilly, but some kids do experience it; accents tend to go away after a while; I now speak English with a cockney accent, you wouldn't know I'm an American. Years later, we moved from Holland to the UK with my job and our twins didn't speak much English, our daughter got a bit of a hard time until they realised that her twin brother was more than willing and able to look after his sister; as they say, blood is thicker than water.
There is no guarantee you will get in your local school, particularly if it is well-performing, so popular. Do your research before you go, use Google maps to find the schools, then local FB groups may be helpful. You may find other US families in the area.
Rent just covers the monthly rent for the property and includes nothing else. Council tax basically pays for local services, like trash, police etc. It's down to the occupant to pay it. How much council tax you pay depends on the "band" your house has been classified in and then is directly related to the value of the house; you can find out about Glasgow council taxes by following this link. Charges for water, electric and gas are also in addition to your rent and council taxes and are again down to you to pay.
A good reference to check out and compare costs and other social details is the Numbeo website; while Downingtown is featured in the data set, there is not a lot of data in there, so I've done a comparison between Philadelphia and Glasgow; this link will take you straight there. The data is probably 6 months behind the curve, but it gives you a good feel as to what goes on.
The thing going on at the moment which is really screwing up everything is COVID; right now I wouldn't recommend moving as it's making life a bitch for most of us and if your desire is to travel while here, probably best to wait out the storm where you are until they get a vaccine sorted out and things calm down.
At the top left-hand corner of the page is a link to our Discover section, this contains our Scotland Guide, just mouse over the "Discover" and you'll get a drop-down menu and the Guide is in there. Read it and any links it gives for general information.
Once you have done that, if you have any further specific questions, please come back to us.
Hope this helps.
Cynic
Expat Team