Remove or cover the finder objective.
Shroud the tube to avoid stray Sun rays when moving the 'scope toward the Sun. I would never observe the Sun with an open telescope especially with a third party and especially with a school group.
Ensure the filter cannot fall off. If using an off-axis filter ensure the remaining aperture is completely covered.
Never leave the telescope unattended.
Ensure you or the school have adequate third party insurance.
Explain the dangers of solar observing and what will happen if the filter comes off.
I find group viewing with a non-tracked telescope difficult particularly with school groups that want to put their hands on everything. May I suggest a small 80mm refractor on a mount that tracks in RA. Once aligned the image will stay in view.
A white light solar filter will show you sunspots (if there currently are any) but not much else. A special Ha solar telescope such as the PST will show you prominences and surface detail. The PST utilises a special narrow band hydrogen alpha filter. More expensive versions with even narrower filters show the surface detail even better but the flares are fainter.
A PST would be a good investment for a school science section.