Coloured pencils not felt tip pens

[Northumberlandlass]

I have a genuine question. DS came back from school today with last weekend's maths homework. It was a large grid of 100 squares , he had to colour in a symmetrical (sp?) pattern.

He LOVES patterns an eagerly completed it with a large selection of pens (various) colours. He worked really hard and it was fab! The comment from his teacher read "Well done. Please use colouring pencils".
I am confused, why are pencils preferred to pens?

TIA

Could the pen ink rub off and stain other things? (Maybe grasping at straws here)

Pencils are harder work on the hand muscles to use - maybe she wanted him to do a hand workout!

because pens make a godawful mess of clothes - many schools prefer colouring pencils only except for art etc when they've got aprons on

My dd's lovely - and very experienced - year 3 teacher banned felt tips because he had seen too may children ruin work they had spent ages on becaue the pens marked the page underneath, IYKWIM.

As a teacher, I hate felt tips. I have banned them, but the pupils persist.

I hate that they go through the paper and are too overwhelming. I prefer work to be lightly shaded.

If it is for maths things as opposed to art could it be that they may need to rub out if they make a mistake?

It was on a maths worksheet that was completed at home and then stuck into his maths book. I appreciate the fact that if used directly onto the page in his book, the ink would go through onto the next page.

Thanks for the responses ladies. I appreciate that their are much bigger issues to discuss on Mumsnet

Also, whr they start doing science diagrams they will need to be able to shade - maybe the teacehr is starting them off on this idea?

if you colour in pencil crayon you can still clearly see the printed numbers whereas with felt tips they are obliterated