Dell Vostro 3500 Not Charging The Battery

We have a Dell Vostro 3500 which is not charing the battery when it is plugged into the mains.

Checked/swapped and not the cause:

Battery
Mains lead [from socket to power brick]
Power brick [from mains lead to laptop]

The laptop is out of warranty by about 6 months. It seems a waste to say that this is of no use now but it will be too expensive to have repaired as the cost is likely to be approaching half the cost of a new one [seen as uneconomic to repair]

What else could I try to get this back into the classroom and in use by the students again?

Thanks.

Likely to be a charging circuit failure - this is part of the mainboard on lower end Dells so won't be fixable :(
Cheapest option is buying a new/refurb board from eBay.