It's actually happening. You, my little boy, are going off to 'big school'. How did this day creep up on us so quickly?

Well, partly because it actually IS so very very soon. You're only three. Three!? What three-year-old has any business in an institution that also houses tweens who know all about Snapchat, and selfies, and all the things I desperately want to shelter you from for as long as possible?!

Your entry into the world is so recent that I still have the muscle-memory of cradling you in my arms, still just about retain the bicep strength that was non-existent before your warm little body came along. 

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You still drink milk, from the same type of bottle that you had as a baby (we'd better not tell your big school that).

You still wear a nappy at night and have accidents from time to time when you just forget to go to the toilet (We'd better warn your big school about that, actually...).

You haven't quite mastered getting yourself dressed and can't yet tell your left shoe from your right shoe. Will you be able to find your feet? 

I know the schools are good, I know all the learning is through play, that the teachers are lovely and the playgrounds are separate so that the little people's 'big school' is actually just a large version of a nursery environment. I know that you will be OK, that you are confident and friendly and that you will probably barely notice the transition. 

But I also know how sensitive you are.

How, when other children push in front of you on the ladder up to the slide, you stand back and say, "OK, you first", and keep doing that time and again so that you might never get your turn if I don't interject.

I know how you only like happy stories, and how even gentle Disney films like Frozen are "too scawee" for you to watch.

I know how you feel awkward when you're put on the spot, and sometimes do a dinosaur roar or turn your head rather than say hello when a new adult introduces themselves.

I know how you hate all the attention to be focused on you and how your shyness can look like naughtiness if people aren't tuned into you.

I can translate your toddler ramblings and body language in a way surely no busy teacher of 25 three-year-olds - however wonderful - will have time to do...

Will you be able to open your own lunch by yourself? Will you finally get the hang of putting on your socks? Because at three years old you are now entering a system that will house you for the next 15 years, and there's no going back. Why the rush?

But what I also know is this: you will be more than fine, and you, at least, are ready for your next step.

I'm the one who is going to struggle, with the early mornings, with the anxiety about a future you can't possible conceived of. You're just starting school and I'm already fretting about internet safety and your future relationships and which career you might want to go into. It's my job to shelter you from my worries and I need to pull up my own socks before I expect you to do anything of the sort. Even as I want to cling you to my chest and shower you with kisses, I want you not to need that from me, to be able to rush into your new classroom without giving me a second glance.

I've never been the perfect parent - the one serving up only organic veggies for dinner and making wholegrain bread from scratch. But I did make YOU from scratch, and that tug of war between wanting you to learn things for yourself and the desire to tie up the world into a safe, neat little parcel for you so that you never have to experience pain, or confusion, or fear, is always in flux. 

They say that deciding to have children is like deciding to have your heart forever walking outside of your body. It's true. And now my heart is stomping bravely across sand in new school shoes, into a place that I can't parcel up neatly any more, because the whole point is that your universe is about to expand indefinitely. A time of growth for you, but in a small, selfish way for me, a time of loss.

Tabitha is the editor of Baby & Child magazine