I was recently asked this question, "which asanas do you reccomend while or after having/had a lumbago respectively sciatic pain???"
Here was my response: let me ask you first a couple of questions: are you the one feeling the pain? And, have you had it checked out yet with a professional? (How do you know that the sciatica is caused by the lower back?)
Lumbago is a general term used to describe lower back pain, often sharp sudden pains, but also the term is applied to any lower back pain. Unfortunately, lower back pain can have many different causes. Sciatica is often felt through the legs: it can be caused by lower back disorders (among many other causes) but you seem to imply that you (or a student) are experiencing both lower back and leg pain…is that it?
Often (but not always) sciatica caused by lower back disorders is due to some disc herniation, and the bulging of the disc presses against the spinal nerves, in this case the roots of the sciatica nerve. If (and I stress "IF!") this is the cause, then some therapeutic yoga postures could include Sphinx and Seal poses, to help push the herniation back to its normal position and thus relieve the pain.
Strengthening the core of the body can also help: but it should be done intelligently. Many people have overdeveloped stomach muscles and not strong enough side stomach muscles (the obliques) and back muscles. Crocodile and Side plank can help here. Balancing Cat (also called Bird Dog) and Awkward Airplane can help: in all these the lower back is kept neutral.
Hope this helps.
Cheers
Bernie