When should I disclose my disability?

Should I reveal the fact that I use a wheelchair when completing application forms for work experience?

I have wanted to train as a lawyer since starting my GCSEs and am now in the first year of my law degree. I hope to start applying for law-related work experiece very soon but am worried that my disability will put employers off. As such I was wondering when or indeed if I should disclose the fact that I use a wheelchair? If you are going through a similar experience or have managed to secure a training contract/vacation scheme despite your disability I would love to hear from you.