We are happy to try and assist school groups - at any keystage - who are studying some aspect of Astronomy.
As a research-focused working university department, we do not have a dedicated outreach centre - however we can sometimes accommodate group visits. Usually this could include a talk (at an entirely age-appropriate level) followed by Q&A in the lecture theatre, and the chance to visit a historical telescope on site. We offer this for free to schools; but realise that the possibility of this option is strongly constrained by the availability of both staff and lecture theatre during the University term-time.
This is a more flexible option, where an astronomer could come and visit your class in school - to give a relevant presentation, answer questions that pupils have about astronomy and space... Again, this is subject to availability of staff, particularly during University term-time. There is no fee charged, but we would ask that all travel expenses (eg, train fare, mileage at 45p/mile) are reimbursed.
Although we do have a number of enquiries from secondary school students for work experience, please note that unfortunately we are not usually able to accommodate such requests.