Had this happen to me. People will get on through the back door as if they are part of my party. I will tell the driver they are not with me and say that my husband is the only one with me if he is. Sometimes it is just me. Not adding any family.
This has happened to us quite often too. At times, our party has looked like 10 or 12 because of hangers on or people with strollers who took advantage of the door being open to seek on.
This has happened when our actual group was 3 and when our actual group was larger, but only 2 boarded from the back and the rest waited in line.
It has happened Both at bus lines and in attractions - the 'best' attraction is Killimanjaro Safari where we have had people behind us tell the CM they were with us.
We said they were not, so they said, "we didn't mean them, we meant the group ahead" ( who also said they were not with them ). This has happened several times on the safari. I think the best punishment would have been to make them come with us. That particular day, we waited in the 'special line' for 30 extra minutes compared to what those people actually would have waited.
Maybe the issue of the larger groups has to do more where people are staying and not that it is happening all over the parks. Maybe because people are staying at the value resorts, where bigger groups can afford to stay (or choose to stay), that is where the whole issue is.
I have not stayed at any of the value resorts, but have stayed at the moderate, deluxe, and DVC, and have never seen of the type of abuse that is being discussed here. Also the time of year could be a big issue too.
I agree that it's more likely to be a problem at the value resorts - because that's where more of the complaints posted about have been - for whatever reason.
Larger groups are less likely to rent cars or vans than small groups, partly because they would not all fit.
WDW has always had 'group' for guests with disabilities defined as a total of 6 people. Enforcing it is up to driver discretion. The signs at resort bus stops do say the party total is 6 people.
There are probably as many reports of people with wheelchairs being denied entry or ignored, even when the bus is not full. But, those are noticed by people with disabilities and probably passed over by other readers.
Correct me if I'm wrong, (quite often I am

) but does the law not state in the ADA that if all the places for WCs are being used and there is no available space for WCs then the bus is considered full, and no other able bodied people are allowed to board?
If this is true, then the next bus would board the next person in line which would be the WC first, and the able bodied people would board next. I'm thinking is equal access.
buses nd other forms of transportation are covered under transportation laws (not ADA), but do have some ADA-like provisions.
A bus driver who is/was a DIS had told me that was what drivers we're taught and he sent me a link, which I lost and was never able to find again. I think it was part of a settlement between and city and some people with disabilities who were consistently denied access when there was room. The drivers were loading walking guests first and then saying there was no room or the guest in the wheelchair - even when that guest had waited through several buses already.
Most WDW bus drivers are nice, but we have encountered some who just do not want to load a wheelchair.
- drivers who came out of the bus to tell us (very quietly) that they could not load the wheelchair because the wheelchair seats had people on them ( there were less than a dozen people on the bus, so many vacant people).
- a driver who was talking to a guest who stepped onto the bus for a full 5 minutes (not giving directions or nothing, just shooting the breeze). He was actively avoiding looking at us, ignored us and when he was done talking to that guest, said he could not load DD's wheelchair because wheelchairs have to be loaded first and he already had guests on the bus ( all of 5 guests) so we would need to wait or the next bus.
These are just 2 examples of many we have experienced over the years. I have read similar stories by other posters or had PMs with the stories.
For every one "12 people boarded with the wheelchair" there is probable a matching "the driver would not let us board for no good reason" example.