I feel like that’s somewhat cheating the system if they don’t allow you to use spell check?
I did one today using the TopScore platform and didn't use Word. My reasoning behind this was that if they can track real-time what you're writing then it might look odd if suddenly an answer appears with three minutes to go.
A written exercise is also meant to test your grammar and spelling, so might be best to be honest and do it properly!
Just my 2 cents
I find that sometimes, some responses here have unnecessary and quite insulting implications. I'll have you know I was the spellathon champion 5 years in a row in secondary school 😂. I thought using Word would be pretty common. I have no idea what TopScore's tools are. If I knew TopScore explicitly didn't allow for spell check then I would not have asked.
Such implications don't just apply to me btw, I have read quite a few messages here where people ask for help and are indirectly insulted in response. Let's just all try and actively be helpful without passing judgment.