WFG - sorry to hear you are having problems, as with all of I am speaking from experience of a sample size of 2 (+ a few in the family who have had "interesting educational experiences!
You have to look at what you want out of his education. cos whatever it is at the moment it isn't what he wants... some kids struggle with too much parental attention and concern - he will also be getting that if the class sizes are too small as well, can't jog along....
Light touch parenting is the ideal but obviously helps if you have to have a light touch child too - that tends tio start at about the age of 3 days..
I appreciate you want him to succeed at school, but if there is too much pressure then he will rebel sooner or later ... one relative waited until after public school and oxbridge and professional training to decided he was going to write music instead - much steam from parents ears but TBH you could see it coming from prep school. Some will manage the rebellion big time at Uni.
So if you go for the light touch low maintenance, try the local day school, forget the fees, don't give him any baggage to go with and see what happens - you might be pleasantly surprised.