You can, it is quite correct. There is nothing wrong with this sentence. However, native speakers tend not to use this form very often in conversation. In informal situations, we are more likely to say:
There are a lot of students.
Perhaps you are confusing this with what you have been told about 'much'. It is true that we very rarely use 'much' in positive sentences. While the sentence 'There is much money' is technically correct, it sounds very old-fashioned and unnatural, and a native English speaker is unlikely ever to say this. In informal contexts we'd say
There is a lot of money.
Meanwhile in more formal contexts, we'd rephrase as, for example:
There is a great deal of money.