For me (1) "make mistakes" is the better phrasing. Also "make a mistake" if there is only one.
Phrase (3) does not read correctly. In that context "mistake" needs to be followed by the type of mistake. Eg "I always mistake verbs for nouns when..."
The only usage of (2) "do mistakes" I can think of is as a question, eg "Do mistakes in grammar lead to ...?"
The first line of the question asks "Do you see the mistake in it?" This also does not read nicely to me. Perhaps a better phrasing would be "Do you see the differences between:" or "Can anyone [please] explain the differences in the following:"
(AmE) I don't use or hear "agemate" or "batchmate". I might understand what you mean by "agemate", but definitely not "batchmate". Personally, "batchmate" sounds like computer programming jargon.
If it interests you, please consider the following expressions.
- We are the same age.
This does not imply that we were born on the same day in the same year. It doesn't even imply we were born in the same month. I think most would agree that it implies that we're are about, at most one year apart. For example, we are both 25 years old.
- We are both X years old.
This is pretty clear: we've been alive for (at least) X years. Maybe I am closer to 26, and the other person just turned 25, but we are both 25 years old.
- We're about the same age.
This is bit ambiguous, but I think you can certainly use it if two of you are about 2 or 3 years apart in age.
- We are X years apart.
- We were born X years apart.
4 means that the difference between my age and another person's age is X years. 5 might be used by siblings.
As others have mentioned regarding your other requests, you might consider contemporaries and classmates.
In college and high school, students are often called
- Freshman (plural, freshmen; first year student)
We're freshmen!
- Sophomore(s) (second year student)
- Junior(s) (third year student)
- Senior(s) (fourth year student)
In college, students are also called first/second/third/fourth/etc-year students. Sometimes, the word student(s) is omitted.
- We're first-year students!
- We're first-years!
Best Answer
The word classroom exists and so you should use it, but whether "class room" is enough of a mistake to raise is doubtful. There are quite a few words that were spelled with a space 100 years ago, but are now written without a space. For example "to day" used to be written with a space.
So if this is the only mistake you can mention it, but it is really picky, and you are probably better letting this one pass.