Very hard to say. My school is brilliant - but they did their best to put us off when we applied.
The new league tables are out. Be very suspicious of any school that has a low number of SEN students. Say anything less than 20% and I'd assume kids with SEN were being pulled out of that school.
Equally I'd be a bit suspicious of anything with very high league table results. May well be down to pressure and hot housing which wouldn't suit your DC?
Find out who their SENCO is. They vary from full time non teachers, to teachers doing it on top of their full time teaching job... Obviuosly a dedicated SENCO is the best.... (To give you an idea, ours is only a SENCO, but she only works 3 days a week)
Not sure what SN your dc has, but another factor for us was that our school had a lunchtime club for children who needed extra help at lunch play...
I don't know how you find out when looking round, but the only real diff between my new fab school and my old awful one, is the staff. All of the staff - the dinner ladies, the TAs, the teachers, and the senior staff are all good. They don't just hire any Mum who wants the job as a TA or dinner lady. Whereas at my old school they did just hire any old Mum....
So ask something about the dinner ladies and TAs - but I'm not sure how you can phrase it :)
Good luck. Remember, you only have to choose the best school you can based on the options you have - and the info you have.