Was Ken Tucker 's impression of the series positive ?
Three series were made ( although by Series Three , Tommy was gone — his absence explained by his having decided to join the Navy ) , with several former " Grange Hill " cast members reprising their roles for the spin - off ( such as Linda Slater as Susi MacMahon , Alan 's former school girlfriend , in Series One ; and Michelle Herbert as Tucker 's old class enemy Trisha Yates in the final episode of series three ) , although the programme never came close to matching the popularity of " Grange Hill " .