If you look at a monolingual dictionary, you’ll see that the reading of めじるし for 目標 is outside of what is taught for the joyo kanji. It has that little triangle symbol. So people don’t learn this as part of their compulsory education. If you used it that way, you’d probably need to put furigana if you wanted Japanese people to read it that way.
People don’t often discuss it, but kanji have specific joyo readings. It’s not just a matter of being in the joyo or not being in the joyo. Some readings are excluded as well.
On Kanjipedia, anything in pink is joyo content. So if you look at the readings portion, ひょう is pink and everything else is black.
Some more kanji that have many readings, but some are excluded in joyo
EDIT: On weblio, kanji that are outside of the joyo list are marked with a black triangle, while readings outside of the joyo content have the white one. Here’s an example of both in action. The triangle comes after the kanji it is related to.