I have boys at Eltham, and have done for several years. One in sixth form and one in senior school currently. I've been really pleased with the pastoral care, sport and music, and academic support. There are some excellent teachers and, as with any school, some that are so-so. My sons have felt mostly well-supported academically and I've always been able to contact teachers if I've had any questions. The teachers seem to work very hard to me. There are some teachers who really go the extra mile, taking the kids to academic competitions etc. The music department has historically been very strong. Sport - it's great for rugby, hockey and cricket, swimming, fencing. They do offer football of sorts (Brazilian Futbal I think) but don't seem to have competitive football. They have a climbing wall which is very popular.
Academically their results are similar to or above Dulwich and Alleyn's, depending on which measures you're looking at, but my feeling is it's less socially exclusive. Maybe I'm wrong, but Eltham doesn't feel 'posh' to me. When my Eltham boys go to Dulwich for sports matches they have come back talking about how good the buildings and food are, and how fancy the whole place is. But for us, it wouldn't be worth the journey as I don't want them to spend ages travelling, and tbh for me, I send my kids to school for the education and the quality of life, not for the social networking side. I like the fact that they have schoolfriends who live locally, rather than having to travel miles to get together with their mates from school. I've no prior experience of independent schools so may not be aware of things which others consider important. There are teachers at Eltham who speak very frankly to the children about how privileged they are, which I think is great.
One of my DC went to St Olave's Grammar for sixth form (he was not at Eltham before) and he and his brother at Eltham felt that the quality of life at Eltham was much better, in terms of relationships with teachers and the way Eltham is flexible, not too rule-bound. I had hoped that my other boys would go to grammar schools for sixth form, but they've pleaded to stay at Eltham. I've spent some time poring over local school outcomes and it seems to me that Eltham is less selective than the grammar schools (there are boys who didn't pass the grammar school 11+ there) and yet gets better results than all the grammar schools, with the possible exception of St Olave's Grammar, which is super-selective, and in that case it depends which measure you look at.
Pastoral care is brilliant - there are 2 full-time nurses and a wellbeing centre. You can go and see the nurses at any time if you need a chat or feel unwell, and the nurses can overrule anyone in the school, including sports teachers! One parent told me that her son, who had ASD, used to often go to see the nurses for a chat and juice and biscuits at break and lunchtime, for some ad-hoc counselling. The boys all love the wellbeing staff. The nurses take the sex education classes and these are apparently hilarious and very informative - I was so impressed by how well it was all handled. Loads on positive masculinity, consent workshops etc . When the 'cup of tea' consent video was doing the rounds, the nurses were on it - the boys have to watch that once a year apparently!
There are some children who've had challenging behaviour and the school seems to keep them wherever possible. It's very rare for someone to be kicked out and I've only heard of it happening after multiple chances.
On the downside - the boys are worried about how going co-ed will change the school. The older boys valued the freedom of the school but the current teacher responsible for behaviour/discipline is very strict and has, eg, banned various boisterous games that the boys were playing at break, and has become more strict all round. It seems to be becoming more 'normal' , whereas they've valued the fact that it has been an old-fashioned school.