Well, a lot of what I was gonna say has already been said, but I'll put my $0.02 in.
It really depends on what you see as "Less". Do you mean, treated as a lesser sentient being? Lesser mentally? Lesser physically? Less appreciated? Gotta give us more to go on.
Now, if you mean that they should/are treated as lesser, that they are disposable, its ok to harm them, (etc. with that line of thinking) then yes that is wrong. They are sentient, can feel pain, and even though they may not currently be as equally capable- physically or mentally- as a mature adult, does not mean that they are insignificant, or should be treated as such.
If you are saying that they are mentally and/or physically less capable than an adult then yes you would be correct. We were all at that point before we matured, (assuming we mature) but developing is a process that takes time, and is by no means a bad thing. When just born we are literally helpless, and we do not instantly go into a self-sustaining adult, there is a middle ground, with many varying degrees. But again, this is not a bad thing, all humans go through this process, Edison was once helpless, so was Einstein, as was George Washington, and Ben Franklin, the list goes on indefinitely.
Now if you are saying that they are less appreciated...perhaps they are, I cannot answer that question. Yes there are things that children can do that adults take for granted, and they should not take them for granted, but what realistic steps can one take to appreciate a child more? I'm sure there are ways, but I personally can come up with nothing. And this also depends on the maturity level of the child, if this is a 2 year old we are discussing here, then what realistically can you expect? But if we are dealing with a 10 year old, the situation is a totally different one altogether.