Why is it that there are signs in shul on the women's side to dress modestly in shuls here in Israel but no signs demanding that t he men dress properly? I think it is disgusting & disrespectful that men come into shul on Shabbos wearing shorts & tee shirts & sandals with no socks as it is not a beach,pool or gym!!! No rav goes to shul like that & that should be our guideline not to come to shul like an Arab or Mexican peasant!!!!!
Rav Schulman wrote the following:
"It is not immodest for a man to wear short sleeves, e.g. a T-shirt. We know this because when a Jewish man puts on tefillin, his arm is uncovered to a little above the middle of the bicep.
It is not immodest for a man to wear pants that go down to just above his knees. We know this from the clothing of a regular Jewish priest [kohen] when serving in the Holy Temple. One of their garments was their pants, which reached from the waist to just above the knees. These pants are not mentioned in the list of priestly garments that are described as being worn for "honor and glory," because their stated purpose is for "common decency."
Although for the rest of the year the regular Jewish priests usually also wore a tunic that reached from their shoulders to their feet for more modesty, on the Eve of Passover they wore a just shorter-length shirt and their pants, because of all the blood on the Temple floor from the sacrificial Passover lambs.
The obligation for men to follow their traditional standards of modesty is not as strict as the obligation for women to follow their traditional standards of modesty."
https://www.asknoah.org/forum/showthread.php?tid=9&page=2&highlight=modesty+for+men