A letter to practices on 15 September says NHS England expects to start the vaccination programme in schools 'no later than' the 22 September 'with the majority of school visits completed and vaccinations administered before October half term'.
However it acknowledged the tight time frames involved could mean that some school visits will not take place until after the break.
The letter suggested that some PCN sites might also be 'sub-contracted' by NHS England regional teams to deliver the vaccinations. However it stressed that the jabs could only happen outside of schools as an exception and after NHS England had determined that they would not impact on capacity at vaccination sites.
The letter also revealed that PCN vaccination sites could be part of follow-up vaccination plans for any children who turn 12 after the school visit and those who were absent on the day of vaccinations, within 28 days of a positive COVID result, or take longer to decide to take up the vaccination offer.
It says: 'Further guidance will follow on the expectations of a secondary offer, and the evergreen offer for those turning 12. It is anticipated that this will be delivered out-of-school (to minimise any further disruption to education and other immunisation programmes).'
NHS England said it expected that school-based vaccination teams would also be able to immunise any clinically vulnerable 12- to 15-year-olds and those aged 16 and 17 who had not yet received the vaccine.
It has also suggested that school teams could administer the COVID-19 vaccine at the same time as the flu jab, but stressed that they 'should not delay vaccinations' in order to do this.
The plans follow recommendations from the UK's chief medical officers last week that healthy children aged between 12 and 15 years should receive a single dose of the Pfizer/BioNtech vaccine.
Ministers sought advice from the CMOs earlier this month after the Joint Committee on Vaccination and Immunisation (JCVI) said the benefits of vaccination against COVID-19 'marginally outweigh' potential risks in children aged 12 to 15 years old, but stopped short of recommending adding this group to the national vaccination campaign.
In advice published on 13 September, the CMOs said the benefits of ''educing educational disruption and the consequent reduction in public health harm' from extending jabs to this group - added to the marginal benefit identified by the JCVI - justified rollout to 12- to 15-year-olds.
The CMOs have asked the JCVI to provide further advice on whether a second dose of the vaccine will be needed for this cohort.
The JCVI had previously recommended that young people aged 16 and 17 years old, as well as clinically vulnerable children aged between 12 and 15 years old receive the COVID-19 vaccine. These jabs are being delivered by PCN and other vaccination sites.
Current guidance is that 12- to 15-year-olds in at-risk groups, as well as those aged between 12 and 18 who are a household contact of someone is immunosuppressed, should receive two doses of the Pfizer/BioNTech vaccine at least eight weeks apart. Meanwhile, healthy 16- and 17-year-olds should receive one dose of the vaccine pending further advice from the JCVI.