Collaborative practice is hugely important. I am having massive issues with this in a setting I am doing some work in at the moment who expect me to withdraw students to a room on my own and do "magic wand" therapy" once a fortnight.
Carryover is the key. In every setting I have ever worked, the key to good SLT provision is a team based approach. The HLTA I work with in my SLI unit basically makes my intervention work. To give you an example, I work in that setting once a week. On Monday, we were working with a student on curriculum vocabulary. The HLTA had gone to the subject teacher for a list of relevant vocabulary and ask for key information and had prepared visuals and definitions according to a specification I had sent her and laminated these.
In the session, we both went through the key words and presented different ways of learning and remembering the information, putting it into sentences etc. I would demonstrate the teaching strategy for a bit and she would record responses. Then she would present one so I could watch responses, say, and then I would say: "maybe we need to try it like this" and tweak it, or we would accept that as a strategy (she is highly trained, so really most of the time we work it out together). Then we - or rather the student! - did some precision teachingy type stuff based on the targets. I had done some training on this with the HLTA but she was unsure about certain aspects of the presentation of materials, so we did some troubleshooting around this. Then we repeated the process for all 15 words and took data at the end of the session. We then discussed the session and what needed to be in the plans for the week (when I am not in) and how she could tweak etc. She repeated the info for me and wrote it down and I checked it.
This HLTA works with this student every day in at least one lesson. She also works with him for 15 minutes at "tutorial" and at 15 minutes towards the end of the day.
She sees him at break and is the contact person with all teachers, co-ordinating key word collection and assignments etc and she sets homework based on our plans. She also ensures that other support staff who support him in lesson use the same strategies (which I check by observing once a term).
Yes, I could just see him on my own. But he would have one hour of SLT a week instead of one hour of SLT and up to 10 hours of carryover (this is for a very severe impairment in a specialist setting so might not be appropriate for all students with SLCN).
To be honest, I truly believe that in some respects she is better than me at this stage because she has more time with them but has been trained very carefully by me so she will sometimes point out things and ask why x is happening leading to an important adjustment to target. She reports everything to me, it's brilliant.
Contrast this with another setting where basically I am dumped in a room and left to "get on with it" without even access to a student's timetable or a list of their teachers. I'm not seen as part of the school community, requests for meetings are ignored, emails trying to set up training aren't responded to for months. The fact I am registered and qualified doesn't in and of itself enable me to meet the students needs.. I need to know and be able to impact upon the communication environment and make my intervention functional and meaningful, which I just can't do if there is no team working.
Direct involvement from an SLT in a regular capacity is important. I said fortnightly because you said 6 a term and a term is usually around 12 weeks but sometimes more.. but if I were a parent, I would consider it would be best to have ongoing regular input rather than a 6 week "programme" and then a break IMO. They may not find this feasible. I said that other contacts might be necessary on top of this, because they really will if statutory obligations are to be met.
Direct contact is good but in and of itself it won't really maximise results. You need both ideally. I would not settle for direct therapy without a training component, personally.