Not a poor school no, but at an okay + school yes. I think the right placement for secondary is much more important than primary, and find it odd that so many people move heaven and earth in the area I live in to get their kids into the best performing primaries, when actually, all the primaries in the town are fairly good.
I think the most important thing a school can be is a pleasant, supportive environment. If your child is at a school with not the greatest facilities - but the teachers and pupils are generally lovely - I think this is today the most important thing. Because let's face it - a child can access literally all the books and information in the world at their finger tips! And there has to be internal motivation for success long-term.
I have a relative that went to one of THE public schools and came out with B's & C's despite all the cultural experiences, high quality tuition and tiny class sizes. He didn't manage to do much networking to any great degree either, and now has a pretty standard office job.
Also, have two relatives in entertainment. One failed the 11 plus but is hardworking and making a good salary in their mid 20's. The other went to grammar school, spent about 15 years in further education, has loads of qualifications, but has now given up on the academic career and is entry level in the entertainments business, well into their 30's.
I personally would avoid schools with accounts of bullying like the plague. Also, I think smaller sized schools are generally much better unless a child is particularly outgoing and confident.