Is it a high-quality source? Is it accurate?
The quality of any particular article will depend upon who has taken an interest in the article. Some articles are excellent; others seem randomly focused on particular issues. Although it may be considered a fairly accurate source, there have been many cases of false information appearing in Wikipedia articles.
While all information in Wikipedia articles is supposed to be cited, many articles have insufficient citations or none at all. This question of quality control is the primary reason why you may be told by your professors not to use it as a source for your academic research.
Wikipedia can be a helpful resource to familiarize you with a topic and can be a good starting point to acquire background information on your topic. As with other encyclopedia sources, Wikipedia is not generally considered an acceptable source in academic research. Whenever possible, find an alternate source for your research assignment. If you have trouble finding the information you need elsewhere, just ask your librarian for help!