If you factor in how many holidays teachers get, then it's the equivalent of working 4 days a week for a full year (assuming 4 weeks holiday in an office job).
I know how full-on the terms are, (secondary English myself) but the holidays are truly a huge boost compared to any other job.
You sound like you don't know what you want - you start by saying that you want more cash to pay off debt, then mention cutting down to 4 days a week. But financially, the best investment is pension. Unless you know that you have a life-limiting illness, pension is what you should do.
Your kids see you as much as other kids see other working parents, AND have the holidays. You are making ends meet each month, rather than getting further into debt. Why would you want to jeopardize what sounds like a pretty stable situation? It's hard work, of course it is, but you are raising kids and building for a future. Unless the debt is so crippling that it is actually growing, the best financial decision is to keep paying into the pension.
If this is about something else - being too tired, missing your kids etc, then you need to ask a different question. But from what you've posted you'd be risking ameliorating your current financial pressure by actually making your life considerably worse in the future.