Is it permissible to conceal knowledge—that is not Shar'i (Islamic)—in order to obtain higher grades, and does that affect the outcome? And is saying to one's mother, "I am studying for the exam," when she asks for something, considered an act of disobedience (ʿUqūq)? And which takes precedence: obeying one's mother or performing the obligatory prayer on time?

Concealing worldly knowledge does not fall under the threat (of punishment), but it is better to impart it.

Concealing knowledge is a disliked cause, while imparting knowledge is an act of worship, and worship is a cause for success.

If your mother asks you for something while you are reviewing your lessons, you are obligated to answer her. You may be sinful for not answering her. If you are short on time, you can politely ask her permission to delay the answer.

There is no doubt that performing the obligatory prayer at the beginning of its time is better than delaying it, but it is not obligatory. Therefore, you must answer your mother first, then pray.