no its not but tell them you are already in the middle of the school term, so you can start working once the semester ends. However, it’s ultimately up to the employer whether they’re willing to wait for you. Since you’ve already received your EAD card, you’re legally authorized to work. If you’ve also filed your I-485, you generally no longer need to maintain your F-1 status and can choose to withdraw from your classes if you wish. Just make sure you’re comfortable relying on your pending adjustment of status rather than your F-1 status before making that decision.

by the way, if your I-485 has been pending for more than 180 days, you’re generally in a much stronger position. A properly filed, bona fide I-485 provides you with a period of authorized stay while it’s pending. Also, keep in mind that some employers may try to pressure you into staying by telling you they’ll withdraw your I-140. Don’t let that alone scare you. If your I-485 has been pending for more than 180 days and you’re otherwise eligible, the withdrawal of the I-140 does not automatically mean your adjustment of status will be denied. In many employment-based cases, you may be able to keep your case alive by using job portability and moving to a same or similar position with another sponsoring employer. Every case is different, so make sure you understand your options before making any decisions. Don’t let fear or misinformation pressure you into staying in a job that’s not right for you. good luck!