What do you teach to your student regarding the minimum safe altitude when on navigation.
MSA is one of the Instrument Flight Rules. Rule 33 in the UK.
For VFR flight look out of the window and fly at an altitude so as to avoid obstacles.
But what do you brief them if the wx deteriorate and they have to fly low level below a cloud base.
Your Operations Manual should detail a minimum altitude for VFR flight and if the weather is likely to deteriorate below this you do not authorise solo flight.