This will be quick.
When considering certain interventions and activities for learners with developmental disabilities, it is important to remember two questions for the learner's dignity and ability to learn. Is the activity age appropriate? Is the activity age respectful?
Not sure? We'll, here's the difference.
Age appropriateness refers to the learner's developmental age. If a learner is 11 years old, but is developmentally about 5 years old, then reading kindergarten books and engaging in certain activities with others who are more their developmental age is, you guessed it, age appropriate. There is no concern for age respectfulness, because the learner could not read at level and may struggle socially with children who have met their milestones by age 11.
Some kindergarten aged learners may carry around little toys or a blankey. The same 11 year old referred to above should NOT be doing this. It does not respect their actual age. They should not be out on community outings and holding hands in line with 5 year old children. An 11 year old carrying around a Barney doll is like putting them in a shirt that say, "I am a actually 11, but am developmentally 5." It is undignified, and, to be glib, will not help them make friends with their peers.
This does not mean that opportunities with similar aged peers should be excluded, or that inclusion in the general education classroom should be neglected. (This author is 100% for inclusion as much as possible. Hopefully always.) These are merely examples. Please task yourself to think of examples when considering the differences between age appropriateness and age respectfulness.