Is it permissible for a Muslim to study in a college where there are crosses on the walls of the classrooms?

Firstly: 

In the answers to questions no. 135279
and 121170 we explained the ruling on making
crosses and putting them on clothing or walls, and the difference between
the cross which it is forbidden to make or hang up, and that which resembles
it but is not regarded as the kind of cross that it is prescribed to remove
and is prohibited to buy, sell or hang up. 

Secondly: 

With regard to these images in the form of a cross that are
hung up in classrooms and lecture halls, we should examine the matter first
of all, and determine for what purpose they were made. Are they made to look
like the cross which is a symbol of Christianity, or are they just patterns
and adornments on the wall, or design elements that look like crosses? 

If they are the first type, then what is prescribed is to
dismantle and remove them, because they are symbols of the Christian
religion, and if the Muslim is able to remove them himself, then what is
prescribed is to remove them, and he should forbid putting them up, because
of the report narrated by al-Bukhaari (5952) from ‘Aa’ishah (may Allah be
pleased with her), that the Prophet (blessings and peace of Allah be upon
him) did not leave anything in his house on which there were crosses but he
removed them. 

Al-Haafiz (may Allah have mercy on him) said: 

Because the cross is something that is worshipped besides
Allah. End quote. 

If it is of the second type, which is if it is a kind of
pattern and adornment, or design elements that is not intended to look like
crosses per se; rather it is something that happened coincidentally, then it
is not required to remove it. But it is a good idea to change it so as to
avoid any resemblance to crosses. 

Thirdly: 

If it is of the first type which is forbidden, then what must
be done is to change it by taking action and removing it and forbidding it,
if it is possible to do so. If it is not possible to do so, or if removing
will lead to greater harm or trouble, then what one must do is denounce it,
forbid it and encourage its removal verbally. If it is not possible to do
any of that, then one must disapprove of it in one’s heart. 

Muslim (49) narrated that Abu Sa‘eed al-Khudri (may Allah be
pleased with him) said: I heard the Messenger of Allah (blessings and peace
of Allah be upon him) say: “Whoever among you sees an evil action, let him
change it with his hand (by taking action); if he cannot, then with his
tongue (by speaking out); and if he cannot, then with his heart (by
disapproving of it and feeling it is wrong), and that is the weakest of
faith.” 

In the answer to question no. 12812,
we explained that if denouncing an evil will lead to a greater evil, then it
is not permissible to denounce the one who does it. 

In the answer to question no. 96662,
we explained that one of the conditions of enjoining what is right and
forbidding what is wrong is that the Muslim should be able to do that
without bringing harm upon himself. If it will bring harm upon him, then it
is not obligatory for him to do that, because everything that is obligatory
is dependent upon being able to do it. 

If the administration of the university insists on not
changing or removing these crosses, then the Muslim must continue to
disapprove of it in his heart, and if he is able to change his place of
study without that being detrimental to his interests, then he should do
that and his reward will be with Allah. 

What is prescribed is for the Muslim, in the first place, to
choose a suitable environment in which to live and study, and if he is faced
with something contrary to that and is not able to change it, he should
denounce it and disapprove of it according to what he is able to do, and
there will be no blame on him. 

For more information, please see the answers to questions no.
112188 and 127946 

And Allah knows best.