You asked

What if my child with learning disabilities doesn't get the necessary help in secondary school?

In general, your child’s individual education plan (IEP) is the map that documents exactly what services your child will receive, when he will receive them and from whom. The IEP is the best way to ensure that your child is getting the services that they need. IEP’S will eventually become legally binding documents which ensures the school must provide the services outlined within.
An IEP cannot be changed or altered in any way without your consent. If you have any concerns don’t be afraid to speak to the school principle because he will be responsible to see to it that children are receiving th services they need and are entitled to receive.
What are my options if any difficulties arise?
If there are any concerns about the care that your child is receiving, you should speak to the year head and voice your opinions.The Special Needs Organiser (SENO) assigned to the school should be notified as well as their special education teacher. A meeting may be called upon within a reasonable timeframe. You will be entitled to attend and any concerns you may have can be discussed.  If this meeting doesn’t resolve your concerns then you can contact the National Council for Special Education for further information and support.
It is important to take things one step at a time, speak to your child’s special education teacher and be clear about your concerns. Be assertive but not aggressive as everyone is doing the best that they can. Have your child’s IEP in front of you when you speak to the teacher or the other staff members. Remember, that you have a right to appeal as outlined in the NCSE and SESS websites.Try not to rush to judgement, try and work things out before threatening to appeal. The next most important port of call will be with the Special Needs Organiser assigned to the school.

More questions

Your child will have an Individual education plan that outlines exactly what services your child will receive.
Any child who received special education resources or support in primary school will almost certainly be eligible for the same support in secondary schools.
If your child has been receiving extra help in primary school it is important to look for a secondary school that will suit his needs
There are significant differences between children who are slow learners and children who have a learning difficulty?
There are lots of things you can do to help your dyslexic child develop their reading skills.
It's perfectly normal for parents of children with ADHD to worry about their child's future. 
Teenager's with ADHD will require additional support and supervision from parents to avoid behaviour problems.
There is no single, easy way to treat ADHD. Treatment is made up of a mixture of medication, parent training, counselling and a special education environment.
ADHD is generally diagnosed when a number of the symptoms outlined before the age of seven and for a period of more than 6 months. 
There are many different behaviours which are characteristic of ADHD: