If your child is starting in reception at a state school, they are entitled to full-time education from the beginning of the Autumn term.
You can choose to send them part-time before they reach compulsory school age, but the school cannot insist that you do. Many schools present parents with transition arrangements which may be a later start, weeks of alternating mornings and afternoons, or gradual attendance building up to half term. Schools tend not to inform parents that these are optional, leaving lots of working families in the lurch when it comes to children who’ve left full-time nursery or other childcare, and plenty of people take unpaid leave or use up large chunks of their annual leave allowance dealing with the consequences of part-time or late starts.
If this is the case, for you, you can insist that your child begins school full time from day one. Your child has a right to this, if they are at a state school, and there is some very clear guidance from the Office of the Schools’ Adjudicator to explain this.
I’m posting this as my dc’s school had a six-week transition period, which would have meant I had to take all of my annual leave allowance to cover it, as I’d be able to attend work for less than an hour a day. I insisted on my dc’s right to full-time education, and it was fine, and many other parents sent their children in over the next few days, so more than half were full-time way before the end of the school’s transition period. Dc thrived at school, and transition from full-time nursery to full-time school was pretty straightforward all-in-all.